Estado Libre y Soberano de Sonora
Free and Sovereign State of Sonora
Flag of Sonora
State of Sonora within Mexico
State of Sonora within Mexico
Coordinates: 29°38′46″N 110°52′08″W / 29.64611°N 110.86889°W / 29.64611; -110.86889Coordinates: 29°38′46″N 110°52′08″W / 29.64611°N 110.86889°W / 29.64611; -110.86889
Largest cityHermosillo
AdmissionJanuary 10, 1824[1]
 • BodyCongress of Sonora
 • GovernorClaudia Pavlovich PRI logo (Mexico).svg
 • Senators[2]Arturo Bours Griffith Morena
Lilly Téllez Morena
Sylvana Beltrones Sánchez PRI logo (Mexico).svg
 • Deputies[3]
 • Total179,355 km2 (69,249 sq mi)
 Ranked 2nd
Highest elevation2,620 m (8,600 ft)
 • Total2,850,330
 • Rank18th
 • Density16/km2 (41/sq mi)
 • Density rank27th
Time zoneUTC−7 (MST[7])
 • Summer (DST)UTC-7 (No DST)
Postal code
Area code
ISO 3166 codeMX-SON
HDIIncrease 0.806 Very High Ranked 4th out of 32
GDPUS$ 16,416,142.57 th[b]
WebsiteOfficial Web Site
^ a. Joined to the federation under the name of Estado de Occidente (Western State) also recognized as Sonora y Sinaloa.
^ b. The state's GDP was $210,126,625 thousand of pesos in 2008,[8] amount corresponding to $16,416,142.57 thousand of dollars, being a dollar worth 12.80 pesos (value of June 3, 2010).[9]

Sonora (Spanish pronunciation: [soˈnoɾa] (About this soundlisten)), officially Estado Libre y Soberano de Sonora (English: Free and Sovereign State of Sonora), is one of 31 states that, with Mexico City, comprise the 32 federal entities of United Mexican States. It is divided into 72 municipalities; the capital city is Hermosillo. Sonora is bordered by the states of Chihuahua to the east, Baja California to the northwest and Sinaloa to the south. To the north, it shares the U.S.–Mexico border primarily with the state of Arizona with a small length with New Mexico, and on the west has a significant share of the coastline of the Gulf of California.

Sonora's natural geography is divided into three parts: the Sierra Madre Occidental in the east of the state; plains and rolling hills in the center; and the coast on the Gulf of California. It is primarily arid or semiarid deserts and grasslands, with only the highest elevations having sufficient rainfall to support other types of vegetation.

Sonora is home to eight indigenous peoples, including the Mayo, the O’odham, the Yaqui, and Seri. It has been economically important for its agriculture, livestock (especially beef), and mining since the colonial period, and for its status as a border state since the Mexican–American War. With the Gadsden Purchase, Sonora lost more than a quarter of its territory.[10] From the 20th century to the present, industry, tourism, and agribusiness have dominated the economy, attracting migration from other parts of Mexico.


Several theories exist as to the origin of the name "Sonora". One theory states that the name was derived from Nuestra Señora, the name given to the territory when Diego de Guzmán crossed the Yaqui River on the day of Nuestra Señora del Rosario ("Our Lady of the Rosary"), which falls on October 7 with the pronunciation possibly changing because none of the indigenous languages of the area have the ñ sound. Another theory states that Álvar Núñez Cabeza de Vaca and his companions, who had wrecked off the Florida coast and made their way across the continent, were forced to cross the arid state from north to south, carrying an image of Nuestra Señora de las Angustias ("Our Lady of Anguish") on a cloth. They encountered the Opata, who could not pronounce Señora, instead saying Senora or Sonora. A third theory, written by Father Cristóbal de Cañas in 1730, states that the name comes from the word for a natural water well, sonot, which the Spaniards eventually modified to "Sonora". The first record of the name Sonora comes from explorer Francisco Vásquez de Coronado, who passed through the state in 1540 and called part of the area the Valle de la Sonora. Francisco de Ibarra also traveled through the area in 1567 and referred to the Valles de Señora.[11] The literal meaning of "sonora" in Spanish is "sonorous" or "loud."


Pre-Hispanic period

Gomphotheres (reconstructed) were hunted in Sonora by ancient Clovis hunters.

Evidence of human existence in the state dates back over 10,000 years, with some of the best-known remains at the San Dieguito Complex in the El Pinacate Desert. The first humans were nomadic hunter gatherers who used tools made from stones, seashells, and wood.[12][13] During much of the prehistoric period, the environmental conditions were less severe than they are today, with similar but more dense vegetation spread over a wider area.[14]

The oldest Clovis culture site in North America is believed to be El Fin del Mundo in northwestern Sonora. It was discovered during a 2007 survey. It features occupation dating around 13,390 calibrated years BP.[15] In 2011, remains of Gomphothere were found; the evidence suggests that humans did in fact kill two of them here.

Agriculture first appeared around 400 BCE and 200 CE in the river valleys. Remains of ceramics have been found dating from 750 CE with diversification from 800 and 1300 CE[13] Between 1100 and 1350, the region had socially complex small villages with well-developed trade networks. The lowland central coast, however, seems never truly to have adopted agriculture.[14] Because Sonora and much of the northwest does not share many of the cultural traits of that area, it is not considered part of Mesoamerica. Though evidence exists of trade between the peoples of Sonora and Mesoamerica, Guasave in Sinaloa is the most north-westerly point considered Mesoamerican.[16]

Three archaeological cultures developed in the low, flat areas of the state near the coast: the Trincheras tradition, the Huatabampo tradition, and the Central Coast tradition. The Trincheras tradition is dated to between 750 and 1450 CE and mostly known from sites in the Altar, Magdalena, and Concepción valleys, but its range extended from the Gulf of California into northern Sonora. The tradition is named after trenches found in a number of sites, the best known of which is the Cerro de Trincheras. The Huatabampo tradition is centered south of the Trincheras along the coast, with sites along extinct lagoons, estuaries, and river valleys. This tradition has a distinctive ceramic complex. Huatabampo culture shows similarities with the Chametla to the south and the Hohokam to the north. This probably ended around 1000 CE. Unlike the other two traditions, the Central Coast remained a hunter-gatherer culture, as the area lacks the resources for agriculture.[17]

The higher elevations of the state were dominated by the Casas Grandes and Río Sonora tradition. The Río Sonora culture is located in central Sonora from the border area to modern Sinaloa. A beginning date for this culture has not been determined but it probably disappeared by the early 14th century. The Casas Grandes tradition in Sonora was an extension of the Río Sonora tradition based in the modern state of Chihuahua, which exterted its influence down to parts of the Sonoran coast.[18][19]

Climatic changes in the middle of the 15th century resulted in the increased desertification of northwest Mexico in general. This is the probable cause for the drastic decrease in the number and size of settlements starting around this time. The peoples that remained in the area reverted to a less complex social organization and lifestyle.[20] Whatever socially complex organization existed in Sonora before the Spaniards was long gone by the 16th century.[19]

European period

Little reliable information remains about the area in the 16th century following the Spanish conquest of the Aztec Empire. Some state that the first Spanish settlement was founded by Álvar Núñez Cabeza de Vaca in 1530, near Huépac. Others state that Francisco Vásquez de Coronado founded a village on the edge of the Yaqui River in 1540 on his way north.[18][20][21] Another source states that the first Spanish presence was not until 1614, by missionaries such as Pedro Méndez and Pérez de Rivas, working with the Mayo.[22] Unlike in central Mexico, no central social or economic centralization occurred in the Sonora area, given the collapse of population centers in the 15th century. The five traditions of the past had broken down to a number of fractured ethnicities. No empire or other system was present for the Spaniards to co-opt for domination purposes.[18][20] In addition, the Yaqui people resisted European intrusion on their lands, effectively keeping the Spaniards out of their area until the 17th century.[23] While exploration of the area happened through the expeditions of the 16th century, significant permanent Spanish settlement did not become possible until the establishment of the mission system.[18][20][24][25]

Jesuit priests began to work in Sonora in the 1610s in the lowlands near the coast. Originally, these missionaries worked out a peaceful compromise with the 30,000 Yaquis allowing for the establishment of more than fifty mission settlements in the Sonora river valleys. This broke down when the Jesuits opposed the native shamanic religious tradition. The Opata were more receptive to the missionaries and allied with them. After this, the Jesuits began to move into Pima and Tohono O'odham territories.[23] Spanish exploration and missionary work was sufficient to consider the territory part of New Spain. An agreement between General Pedro de Perea and the viceroy of New Spain resulted in the general shaping of the province, initially called Nueva Navarra in 1637, but renamed Sonora in 1648.[22]

The most famous missionary of Sonora, as well as much of what is now the American Southwest, was Eusebio Kino.[26] He arrived in Sonora in 1687 and started missionary work in the Pimería Alta area of Sonora and Arizona. He began his first mission at Cucurpe, then established churches and missions in other villages such as Los Remedios, Imuris, Magdalena, Cocóspera, San Ignacio, Tubutama and Caborca. To develop an economy for the natives, Father Kino also taught them European farming techniques.[21][27]

The initial attraction of Sonora for the Spaniards was its fertile farmlands along the river valleys[28] and its position as part of a corridor linking the central Mexican highlands around Mexico City up the Pacific coast and on into Arizona and points north. This corridor still exists in the form of Federal Highway 15.[29] After the establishment of the mission system, Spanish colonists followed. Indigenous response was a mixture of accommodation and violence, as different strategies were employed by different groups at different times. The sporadic violence, which would continue throughout the colonial period, resulted in the Spanish building presidios and other fortifications to protect missions and Spanish settlements.[21][23] While the colonization process was not especially violent, the impact on the indigenous of the area was severe, as it almost completely disrupted their formerly very independent lives, forcing them to conform to an alien centralized system. One consequence of this was alcoholism among the native peoples.[22]

In 1691, what are now the states of Sonora and Sinaloa were joined into an entity called the Provincias de Sonora, Ostimuri, y Sinaloa. They would remain as such through the rest of the colonial period until 1823.[27] At this time, about 1,300 Spanish settlers were in the area.[30] Colonization increased in the 18th century, especially from 1700 to 1767, when mineral deposits were discovered, especially in Álamos. This led to the establishment of a number of royally controlled mining camps, forcing many natives off their agricultural lands. Loss of said lands along the Yaqui and Mayo Rivers led to native uprisings during this time.[22] A major Seri rebellion took place on the coast area in 1725–1726, but the largest uprising was by the Yaquis and Mayos from 1740 to 1742 with the goal of expelling the Spaniards. Part of the reason for the rebellion was that the Jesuits, as well as the secular Spaniards, were exploiting the indigenous. This rebellion destroyed the reputation of the Jesuit mission system. Another Seri rebellion occurred in 1748, with Pima and Tohono O’otham support and lasted into the 1750s. This kept the settlement situation in disarray. With population of the Mexican split half indigenous and half Spanish, about one-quarter of the indigenous population lived in Sonora alone.[31] In 1767, the king of Spain expelled the Jesuits from Spanish-controlled territories, ending the mission system.[32]


In 1821, the colonial era in Sonora was ended by the Mexican War of Independence, which started in 1810. Without being directly involved in the war, Sonora became part of an independent Mexico, which allowed for economic development. The former province of Sonora, Ostimuri, y Sinaloa was divided in 1823 to form the states of Sonora and Sinaloa, with the Sonoran capital in Ures.[27] They were reunited in 1824[26] but became separate again in 1831, when Sonora wrote its first state constitution, which put the capital in Hermosillo. In 1832, the capital was moved to Arizpe.[27]

In 1835, the government of Sonora put a bounty on the Apache which, over time, evolved into a payment by the government of 100 pesos for each scalp of a male 14 or more years old. James L. Haley wrote: "In 1835, Don Ignacio Zúñiga, who was the long-time commander of the presidios of northern Sonora, asserted that since 1820 the Apaches had killed at least five thousand settlers, which convinced another four thousand to flee, forced the abandonment of over one hundred settlements, and caused the virtual depopulation of the interior frontier. ... The state of Sonora resorted to paying a bounty on Apache scalps in 1835."[33]

The struggles between the Conservatives, who wanted a centralized government, and Liberals, who wanted a federalist system, affected the entire country during the 19th century. In 1835, a centralist government was instituted based on what were called the Bases Constitucionales ("Constitutional Bases"). They were followed by the Siete Leyes Constitucionales ("Seven Constitutional Laws"), which remained in effect until 1837. But in December of the same year, General José de Urrea proclaimed in Arizpe the re-establishment of the Constitution of 1824, initially supported by then Governor Manuel Gándara. However, for the rest of the century, Gándara and succeeding governors would support a centralized government, leading to political instability in the state.[21][27] In 1838, the capital was moved back to Ures.[21]

The fertile lands of the Mayo and Yaquis continued to attract outsiders during the 19th century. These were now Mexicans rather than Spaniards, and later in the century, it was a major draw for North Americans.[28] By the end of the 19th century, however, the area received large numbers of immigrants from Europe, especially from Germany, Italy, and Russia, the Middle East, mainly Lebanon or Syria, and even China,[34] who brought new forms of agriculture, mining, livestock, industrial processes, ironwork, and textiles.[26]

The Mexican–American War resulted in only one major military confrontation between Mexican and United States forces, but its consequences were severe for the state. In October 1847, the warship USS Cyane laid siege to Guaymas Bay, resulting in United States control of this part of the coast until 1848.[27][35] When the war ended, Sonora lost 339,370 hectares (13,200 square miles) of its territory to the United States through the Treaty of Guadalupe Hidalgo. Additionally, the war ruined the state's economy.[27] Sonora lost more territory in the 1850s, through the Gadsden Purchase. Before the war, Sonora was the largest State in Mexico. The State lost more than 29,000 square miles to the United States as a result of the 1853 Gadsden Purchase. The majority of the area is today's Arizona south of the Gila River and a part of the present-day southwestern New Mexico.[21] The area's political vulnerability immediately after the war made it susceptible to buccaneers such as William Walker, Gaston de Raousset-Boulbon, and Henry Alexander Crabb, who attacked Sonoran ports such as Guaymas and Caborca. However, most attacks were repelled.[21] The economy did not begin to recover from the war until the late 1850s, when Ignacio Pesqueira became governor and attracted foreign investment to the state, especially in the mining sector, as well as worked to create markets abroad for agricultural products.[27]

During the French intervention in Mexico, Sonora was invaded by French troops as part of the effort to install Maximilian I as a monarch in Mexico. The port of Guaymas was attacked by forces under Armando Castagny, forcing Mexican forces under Pesqueira and General Patoni to retreat north of the city. French troops attacked the Mexicans again at a place called La Pasión, again resulting in defeat for the Mexican resistance. The French were not defeated in the state until the Battle of Llanos de Ures in 1866 by Pesqueira, Jesús García Morales and Ángel Martínez.[26][36] Shortly after this, the state's current constitution was written in 1871, and its capital was permanently moved to Hermosillo.[21][37]

Cajemé, Yaqui resistance leader

During the regime of Porfirio Díaz from the late 19th century to the 20th century, major economic changes occurred. These changes promoted rapid economic growth, which had far-reaching social and political consequences. Sonora and the rest of the northern states rapidly increased in economic importance. Development of a rail system integrated the state's economy into the national, and also allowed greater federal control over all of Mexico's territory. After 1880, this rail system was extended north into the United States, making it an important part of binational economic relations to this day.[38] However, the changes also permitted foreigners and certain Mexicans to take over very large tracts of land in Mexico. In Sonora, Guillermo Andrade controlled 1,570,000 hectares (15,700 km2; 6,100 sq mi), Manuel Peniche and American William Cornell Green about 500,000 hectares (5,000 km2; 1,900 sq mi). Foreign industry owners also tended to bring in Asian and European workers.[21] Chinese immigration into Sonora would begin at this time, and the Chinese soon became an economic force as they built small businesses that spread wherever economic development occurred.[39]

The appropriation of land for both agriculture and mining placed renewed pressure on the Yaquis and other native peoples of Sonora. Previously, active resistance had given the Yaqui fairly autonomous control of a portion of the state and kept their agricultural system along the Yaqui River. Encroachment on this land led to uprisings and guerilla warfare by the Yaquis after 1887. By 1895, the federal and state governments began to violently repress the Yaquis and forcefully relocate captured Yaquis to the plantations in Mexico's tropical south, especially the henequen plantations in the Yucatán Peninsula. The Yaqui resistance continued into the 20th century, with the expulsions reaching a peak between 1904 and 1908, by which time about one quarter of this population had been deported. Still more were forced to flee into Arizona.[40]

20th century

The Cananea miners' strike 1906

The policies of the Díaz government caused resentment not only among the Yaquis, but also throughout the country.[41] One of the preludes to the Mexican Revolution was the 1906 Cananea miner's strike. Approximately 2,000 strikers sought negotiations with American mine owner William Greene, but he refused to meet with them. The strike quickly turned violent when the miners tried to take control of the mine and gunfire was exchanged. Greene requested help from federal troops, but when it was obvious they could not arrive in time, he appealed to the governments of Arizona and Sonora to allow Arizona volunteers to assist him. This increased the scale of the violence. When Mexican federal troops arrived two days later, they put everything to a brutal end, with the suspected leaders of the strike executed. The heavy-handed way in which Díaz had handled the strike made resentment against Diaz grow, with more strikes beginning in other areas.[42][43]

In late 1910, the Mexican Revolution began in earnest, and Díaz was quickly deposed. The governor of Coahuila, Venustiano Carranza, sought refuge in Sonora, and became one of the principal political leaders during the rest of the war, with his main base of operations in Hermosillo. A number of the revolutionary leaders who joined Carranza in Sonora did not come from peasant backgrounds, but rather the lower middle class of hacienda-managers, shopkeepers, mill-workers, or schoolteachers, who opposed large-scale landowners and the Porfirian elite.[44] After Díaz was deposed, Carranza competed for power against Álvaro Obregón and others.[43] The Yaquis joined with Álvaro Obregón's forces after 1913.[41]

By 1920, Carranza had become president of Mexico, but found himself opposed by Obregón and others. Carranza tried to suppress political opposition in Sonora, which led to the Plan of Agua Prieta, which formalized the resistance to Carranza by Obregón and his allies (primarily Abelardo L. Rodríguez, Benjamín Hill and Plutarco Elías Calles). This movement soon dominated the political situation, but it caused widespread political instability in doing so.[45] Obregón deposed Carranza and became the next president of Mexico. For the 1924 presidential elections, Obregón chose to succeed himself Plutarco Elias Calles, who was also a revolutionary leader from Sonora.[46] This effectively ended the war, but hostilities had again destroyed the Sonoran economy.[43] From 1920 to the early 1930s, four Sonorans came to occupy the Mexican presidency: Adolfo de la Huerta, Obregón, Calles and Rodríguez.[26]

The Chinese first arrived at Guaymas in the late 19th century and congregated there and in Hermosillo. Over the following decades, they moved into growing communities such as Magdalena and Cananea. Rather than working in the fields, most started their own small businesses, networking with other Chinese.[34] These business spanned a wide range of industries from manufacturing to retail sales of nearly every type of merchandise.[47] The Chinese in Sonora not only become successful shopkeepers, they eventually came to control local small businesses in many areas of the state.[48] By 1910, the Chinese population in Sonora was 4,486 out of a total population of 265,383, making them the largest foreign presence in the state, with only North Americans a close second at 3,164. Almost none were female, as there were only 82 Chinese females in the entire country at the time. The Chinese population reached its peak in 1919 with 6,078 people, again with almost no Chinese women.[48]

Colonia Centro, calle Pierson, Nogales

Resentment against Chinese success began quickly, and Sinophobia rose sharply during the Mexican Revolution as many Chinese prospered despite the war, and many attacks were targeted against them.[47] The first organized anti-Chinese campaign in Sonora began in 1916 in Magdalena.[49] A more serious campaign began in 1925, calling for their expulsion from the state.[50] Mass expulsions were mostly carried out in Sonora and Sinaloa, partly because of their large populations, but the Chinese, often with their Mexican wives and children, were deported from all over the country. Some were returned to China but many others were forced to enter the United States through the border with Sonora, even though Chinese exclusion laws were still in effect there.[51] Sonoran governor Rodolfo Elias Calles was responsible for the expulsion of most Chinese-Mexican families into United States territory. Despite the diplomatic problems this caused, Elias Calles did not stop the expulsions until he himself was expelled from Sonora. However, by that time almost all of Sonora's Chinese-Mexicans had disappeared.[52] By the 1940 census, only 92 Chinese were still living in Sonora, with more than two-thirds of these having acquired Mexican citizenship. This had the unintended consequence of nearly collapsing the Sonoran economy.[53]

The efforts at modernization and economic development begun in the Díaz period would continue through the Revolution and on through the rest of the 20th century. In the late 19th and early 20th centuries, the process of electrification greatly increased the demand for copper, which led to a boom in mining in Sonora and neighboring Arizona. Cananea grew very quickly from a village of 900 to a city of 20,000. It also led to a network of roads, railroads and other connections across the border.[54] However, organized development of the state's agriculture was put on hold because of the Revolution, the Great Depression and other political upheavals.[55]

In the 1930s, Sonora benefitted from a number of national policies aimed at developing the cities on the border with the United States and at building a number of dams to help develop agriculture and the general water supply.[56] Major agricultural reform was begun in the 1940s in the Mayo River area, when the delta was cleared of natural vegetation and made into farmland. Water for these farms was secure through the building of the Mocúzari Dam about 15 miles (24 km) from Navojoa. When it was completed in 1951, there was a system of canals, wells and highways to support large-scale agriculture for shipment to other places.[55]

In the last half of the 20th century, the state's population has grown and foreign investment has increased due to its strategic location along the border and its port of Guaymas. More than 200 international and domestic enterprises moved into the state, allowing for the development of modern infrastructure such as highways, ports and airports, making the state one of the best connected in the country. A bridge was built over the Colorado River to link Sonora with neighboring Baja California in 1964. One important sector of the economy has been industry, culminating in the Ford automotive plant in Hermosillo and a number of assembly plants called maquiladoras on the border with the United States. One of the fastest growing sectors of the economy has been tourism, now one of the most important sectors of the economy, especially along the coast, with the number of visitors there increasing every year. This has led to a surge in hotel infrastructure, especially in Puerto Peñasco.[56]

Bridge over the Colorado River in Sonora

For most of the 20th century, Mexico was dominated by the Institutional Revolutionary Party (PRI). Discontent with this one-party system became prominent in the northern states of Mexico, including Sonora. As early as 1967, a competing party, the National Action Party (PAN), won control of the city government of Sonora's capital, Hermosillo.[57] PAN won important municipal victories in the state in 1983, which President de la Madrid refused to officially recognize but was forced to let stand.[58] PAN's growing strength by the 1980s forced the PRI to nominate candidates who were similar to PAN, successful business executives who favored economic liberalization over traditional Mexican statism, preferred in the north of the country. Institutional Revolutionary Party won the Sonoran gubernatorial race in 1985, but it was heavily contested with obvious problems of fraud.[59] By the 1990s, PRI operatives caught manipulating election results were actually prosecuted by the Sonoran state attorney.[60] This along with other events in the country eventually led to the end of the one-party system when Vicente Fox was elected president in 2000. PAN has since dominated most of the north of the country, but Sonora did not have its first PAN governor until 2009, with the election of Guillermo Padrés Elías.[61]

Sonora's border with Arizona has received more attention since 2000, with the increase of illegal border crossings and drug smuggling, especially in rural areas such as around Naco, which is one of the main routes into the United States.[62] Starting in the 1990s, increased border patrols and the construction of corrugated metal and chain link fences in California and Texas dramatically cut illegal border crossing in these two states. This led illegal immigrants into the more dangerous desert areas of Arizona and New Mexico, which have mostly seen rises in illegal crossings since then.[63][64] Many migrants now come to the Arizona border between Agua Prieta and Nogales, with Naco as one of the preferred routes for "coyotes" (also called "polleros" or "enganchadores") or smugglers who offer to take migrants across.[62][65] Migrant shelters and hotel in border towns cater to those waiting to cross into Arizona.[66] Providing lodging for migrants is a growing business in Naco and other border towns, where the rate is between 200 and 300 pesos per night per person. Many of these lodgings are filled with people who cannot cross the border.[65] One example is the Hospedaje Santa María, which is a run-down, two-story building.[64]

Picture of the border between Arizona, on the left, and Sonora, on the right

Forty-five percent of the deaths of migrants occur on the Arizona side of the border.[65] According to Arizonan authorities, 2010 was a record year for deaths in Arizona for people crossing illegally from Sonora, with the bodies of 252 crossers found in the deserts between the New Mexico and California borders. This broke the previous record of 234 in 2007, with nearly 2,000 found in this area since 2001.[67] However, Mexican officials state that the figures are higher, with over four hundred dying in Arizona deserts in 2005 alone. In 2006, Mexican officials began to distribute maps of Arizona to Mexicans gathered in Sonoran border town with the intention of crossing illegally. The Mexican government stated the reason for the maps was to help Mexican avoid dangerous areas that have caused deaths from the desert's heat.[66]

Migration and drug smuggling problem has affected most border towns. Many people make a living by catering migrants or working as "coyote" guides.[64] People hoping to cross the border and those recently deported crowd the border area; some of these people return home, but many others decide to stay on the Sonoran border, working to earn money for another attempt. These workers put a strain on insufficient municipal medical services.[65] The walls, which have shut down much of the illegal crossing into Texas and California, have also been built on parts of the Arizona border, especially between towns such as the two Nacos and the two Nogaleses. The wall in Naco is four meters high and made of steel. It currently extends 7.4 kilometres (4.6 mi), but there are plans to extend it another 40 kilometres (25 mi). Security there was further tightened after the 2001 September 11 attacks. The U.S. Border Patrol credits the wall and better surveillance technology with cutting the number of captured border crossers near Naco by half in 2006. People on both sides of the wall have mixed feelings about it.[64]

Violence connected to drug smuggling on the border and in Mexico in general has caused problems with tourism, an important segment of the entire country. Federal troops have been stationed here due to the violence, which has the population divided. While the security they can provide is welcomed, there is concern about the violation of human rights. In 2005, the state began advertising campaigns to reassure Arizonans that it is safe to cross the border.[68][69]

Geography and environment

Natural divisions

Hastéecöla peaks near Bahía Kino

Sonora is located in northwest Mexico. It has a territory of 184,934 square kilometres (71,403 sq mi) and is the second largest state of the country.[37][70] It borders the states of Sinaloa, Chihuahua, and Baja California Norte, with the United States to its north and the Gulf of California to its west.[70] Its border with the United States is 588 kilometres (365 mi) long.[37] The state is divided into five hydraulic regions – Río Colorado, Sonora Norte, Sonora Sur, Sinaloa, Cuencas Cerradas del Norte.[37][71]

The state's geography is divided into three regions created by the rise of the Sierra Madre Occidental mountains and the separation of the Baja California Peninsula, with all three running roughly north-south. The mountains dominate eastern Sonora, while the center is dominated by plains and rolling hills, which then extend west to the coast on the Gulf of California.[37][72]

Center plains and coast

Valley of Sonora

The center plains and coastline were both created by the tearing away of the Baja California Peninsula between ten and twelve million years ago. These plains are between 50 kilometres (31 mi) and 120 kilometres (75 mi) wide, wedged between the Sierra Madre and the Gulf of California, which began to form between 5.5 and 6 million years ago. Climate patterns bring moisture east from the Pacific Ocean, forming rivers and streams that cross the plains area and empty into the gulf. These rivers have brought down sediment from the volcanic rock of the Sierra Madre and eventually buried most of the mountains and hills of the center of the state, smoothing them into plains. These soils are rich in clays and thousands of feet thick in places, making this region very fertile, only lacking water.[72]

The state has 816 kilometres (507 mi) of coastline, all of which faces the Gulf of California, with its relatively shallow and very calm waters.[37] There are beaches along most of this coastline, some of which with fine, white sand. The best known of these are San Carlos, Puerto Peñasco and Bahía Kino. San Carlos, with its Los Algodones Beach is one of the most visited areas on the Sonoran coast. Los Algodones ("The Cottons") is named for its dunes of white sand, which can be compared to cotton balls. San Carlos has a large variety of sea life off its shores, making it popular for sports fishing and scuba diving. A number of Yaquis, Seris and Guaymas on and around the Tetakawi Hill, making a living from fishing.[73][74]

View of San Carlos

Puerto Peñasco is located in the extreme northwest of the state in the Upper Gulf somewhat near where the Colorado River empties. It contains 110 kilometres (68 mi) of beaches on calm seas, located in the Altar Desert near El Pinacate biosphere reserve, with some of the driest climates in Mexico. Since the 1990s, it has experienced large-scale development along its 110 kilometres (68 mi) of beaches, which have calm seas. The area has experienced a building boom since the 2000s.[73] However, as of late 2013, many buildings are vacant, for sale, or neglected due to the suppressed economic conditions and the corresponding decline in tourism.

Bahía Kino is located near San Carlos, with a dock located in the community of Kino Viejo. This bay's beaches have white sand, with warm calm waters off of them. For this reason, Bahía Viejo calls itself la perla del Mar de Cortés ("the pearl of the Gulf of California"). The area is popular for scuba diving and sports fishing as its waters are filled with various species of multicolored fish, small invertebrates, large crustaceans, manta rays, sponges and turtles. On the neighboring islands, sea lions can be seen. Off this coast is the Isla Tiburón, Mexico's largest island and a nature reserve with wild sheep and deer. There are indigenous communities here, especially at Punta Chueca, which still practice hunting, fishing and collecting natural resources, as well as selling crafts to tourists.[73][75]

Lesser known beaches include El Desemboque, El Himalaya and Huatabampito. El Desemboque is a small Seri village with beaches located 370 kilometres (230 mi) northwest of Hermosillo, just south of Puerto Libertad. Activities in the area include scuba diving and swimming in isolated and relatively undeveloped beaches. The current name is from Spanish (disembarkation point), but the Seri name for the area means "where there are clams."[76] El Himalaya Beach is located forty km from Guaymas. It is a semi virgin beach surrounded by calm waters, mountains, and unusual species of flora and fauna and cave paintings. The area is filled with large stone yellow-red rock formations that were created by a volcanic eruption.[77] Huatabampito is an area of beaches in the south of the state. The beaches have delicate dune of fine sand and the waters are clear with a green-blue color. Each year, whales arrive to this area to reproduce in the warm waters. This is the main attraction, bringing visitors from Mexico and abroad.[78]

Sierra Madre Occidental

The east of the state is dominated by the Sierra Madre Occidental, which has less extreme temperatures and, due to the high altitude, relatively more rainfall.[70] As moist air masses move inland from the Pacific and the tropics and are forced against the mountains, they cool and this leads to precipitation, mostly rain but occasional snows in the highest regions. This process takes most of the moisture out of the air and feeds the various rivers and streams, which empty into Gulf as well as underground aquifers that are under the coastal plain.[79]

Flora and fauna

Laguna Náinari

Habitats and vegetation vary greatly depending on elevation and rainfall.[80] An estimated 2,230,000 hectares (22,300 km2; 8,600 sq mi) of Sonora is in arid grasslands; 1,200,000 hectares (12,000 km2; 4,600 sq mi) are covered in forests, 301,859 hectares (3,018.59 km2; 1,165.48 sq mi) in rainforest and 1,088,541 hectares (10,885.41 km2; 4,202.88 sq mi) in farmland. Seventy percent of the territory, or 13,500,000 hectares (135,000 km2; 52,000 sq mi), is covered in desert vegetation or arid grasslands.[37] The Yécora municipality in eastern Sonora has one of the highest grass diversities in Mexico.[81] There are eight types of desert vegetation, seven of which are native to the Sonora Desert and one in the area that transitions to the Chihuahua Desert. Most are scrubs or small bushes, which generally do not reach over 4 metres (13 ft) in height, most of the rest are cactus, with some mangroves and other halophile plants.[37] Many plants are rainfall sensitive, with most trees and shrubs growing leaves and flowers just before or during the rainy season, then drop their leaves afterwards. However, there are plants in flower at one time or another throughout the year.[82] Coastal plants receive less water stress due to lower evaporation rates, and substantial moisture from dew, especially in the cooler months.[83]

View of Isla Tiburón across the Infiernillo Channel

Most forests are located in the northeast of the state, covering about 6.4% of the state. This is the area with the coolest temperatures.[37] Deforestation has been a significant problem, especially after 1980, because the rate of cutting trees has increased. In central Sonora, the area covered by Madrean evergreen woodland and Sonoran Desert scrub decreased 28% and 31%, respectively, between 1973 and 1992 (ValdezZamudio et al. 2000). During this same period,[84] For example, much of the forests of mesquite trees in the lower elevations of the state have disappeared because of the demand for local fuels and the market for mesquite charcoal in Mexico and the United States[85]

Most of northern Mexico suffers from one of the world's highest rates of desertification due to land degradation in arid and semi arid areas, with the loss of biological and/or economic productivity, but the process is most severe Sonora as neighboring Sinaloa. Land degradation occurs because of clearing land for agriculture, the planting of non-native buffelgrass for grazing, the cutting of forests, overgrazing of natural vegetation and soil salinization from irrigation. A study by Balling in 1998 showed higher soil and air temperatures in areas that have been overgrazed, deforested and otherwised cleared land, likely due to the lack of shading vegetation, which leads to higher soil evaporation and desert conditions. Studies have also indicated that warming trends are higher in Sonora than in neighboring Arizona, into which the Sonora Desert also extends.[84]

The state contains 139 species and subspecies of native mammals, with the most important being white tailed deer, mule deer, wild sheep, bats, hares, squirrels, moles, beavers, coyotes, wolves, foxes, jaguars, and mountain lions. Amphibians and reptiles include frogs and toads, desert tortoises, chameleons, gila monsters, rattlesnakes and other types of snakes. The number of bird species native to the state is not known, but major species include roadrunners, quail, turkeys, buzzards and doves.[37]


Sunset over the desert in Sonora

During the Pliocene, the detachment of Baja California, the development of the Gulf of California and the Subartic California current drastically reduced moisture coming into Sonora leading to severe regional aridity in both this state and neighboring Baja California. This created xeric communities and the development of species endemic only to this region.[86]

There are four major climate regions in the state: dry desert (Köppen BW), arid lands (BS), semi moist lands, and temperate zones (Cwb).[87] Ninety percent of the state has desert or arid conditions. The other two climates are restricted to the areas of the state with the highest altitude such as the Yécora area, the mountains north of Cananea and a strip along the southeast of the state on the Chihuahua border.[37][70]

Average high temperatures range from 12.7 °C (54.9 °F) in Yécora to 35 °C (95 °F) in Tesia, municipality of Navojoa. Average low temperatures range from 5.9 °C (42.6 °F) in Yécora to 35.2 in Orégano, municipality of Hermosillo.[37][70] In the winter, cold air masses from the north reach the state, and can produce below freezing temperatures and high winds at night in the higher elevations, but the temperature can then jump back up to over 20C during the day. Freezing temperatures in the lowlands almost never occur.[80][88] In February 2011, the Mexican government recorded a low in Yécora of −12C.[88]

San Carlos during the wet season

Precipitation is seasonal and most occurs in the higher elevations. In hot and arid or semi arid lands, evaporation vastly exceeds precipitation.[89] Mexico's most arid area, the Altar Desert is located in this state.[70] The east of the state is dominated by the Sierra Madre Occidental, which has less extreme temperatures and relatively more rainfall due to altitude.[70] Most moisture comes in from the Pacific Ocean and the tropics, which is pushed against the Sierra Madre. This cools the air masses, leading to rain and occasionally snow in the higher elevations. While most of the rain falls in the mountainous areas, much of this water finds its way back to the western coastal plains in the form of rivers and streams that empty into the Gulf of California and fill underground aquifers.[79] Most of the year's precipitation falls during the rainy season, which is locally called “las aguas” (the waters). These last from July to mid September, when monsoon winds bring moist air from southerly tropical waters. Most of this is from the Pacific Ocean west of Central America but can also come from Gulf of Mexico as well. This moister flow results in nearly daily afternoon thunderstorms. After the las aguas, there may be additional moisture brought in by hurricanes, which generally move west along the Pacific coast of Mexico and occasionally come inland, especially in southern Sonora. However, these storms tend to drop large quantities of rain in a short time, causing flooding and destruction.[83]

In the winter, from November to February, there are light rains called equipatas ("horse hoofs", named after the sound the rain makes). These rains come in from the north from the southern extensions of frontal storms that originate in the northern Pacific Ocean. These end by March or April when the fronts are no longer strong enough to reach this far south. They end even earlier in the extreme south of the state as the storm systems retreat, with the dry season lasting eight or nine months in this part of the state. In the north these rains support a wide variety of spring annuals and wildflowers, but the water they supply in the south of the state is still important to help replenish wells.[83]


Satellite photo of the Colorado River delta in Sonora

With the exception of the Colorado River, river and aquifer systems in Sonora are a result of rains from incoming clouds rising above the Sierra Madre Occidental. This water runs down the west side of the mountains along the canyons and valleys towards the plains and coast and into the Gulf of California,[79] Sonora has seven major rivers – the Colorado River, the Concepción River, the San Ignacio River, the Sonora River, the Mátepe River, the Yaqui River and the Mayo River. Dams, such as Alvaro Obregon, Adolfo Ruiz Cortines, Plutarco Elias Calles, Abelardo Rodriguez and Lazaro Cardenas, have been built along some of these rivers, at least two of them where natural lakes existed.[37][87] Some of the dams formed large deltas, such as that of the Mayo River.[28] The largest aquifers are mostly found between Hermosillo and coast, the Guaymas Valley and the area around Caborca. Most of these are having problems due to overpumping for agricultural irrigation.[37]

Protected areas

Sonora has 18,463 square kilometres (7,129 sq mi) of protected wildlife areas.[90] Protected natural areas in the state are of three types: biosphere reserves, areas for the protection of flora and fauna and areas for the protection of natural resources.[91] The El Pinacate biosphere reserve is located between Puerto Peñasco and the United States border in the Altar Desert. The reserve consists of an area with a series of gigantic dormant volcanic craters, which are covered with flora and fauna. It is frequently visited by foreign tourists, researchers and photographers. The reserve has a site museum, which displays the area history from its formation to the present. The craters are named Badillo, Molina or El Trébol, Cerro Colorado, Volcan Grande, Caravajales and the largest, Mc Dougal.[92]

The Cañón las Barajitas ("Barajitas Canyon") is a protected natural area which consists of three different ecosystems, located 31 kilometres (19 mi) north of San Carlos. It contains a kilometer of beaches and a canyon which has two distinct microclimates, one arid and desert-like and the other subtropical. The area was a wide variety of fauna including whales, dolphins and manta rays that can be seen off the coast depending on the season. Activities for visitors include kayaking, paddleboats, scuba diving and fishing. There are also caves as well as a solor observatory.[93]

The Alto Golfo y Delta ("Upper Gulf and Delta") biosphere reserve encompasses is in the northwest of Sonora and northeast of Baja California Norte at the northernmost part of the Gulf of California and the delta of the Colorado River. The area is home to a very large number of marine species. There are also rocky beaches along with those with fine sand. Some of these are home to groups of seals and sea lions. The reserve was created in 1993 and encompasses an area of 934,756 hectares. On land, there are arid scrubbrush, coastal dunes and an estuary. It extends into the far upper part of the Gulf of California.[94]

The Bahía e islas de San Jorge ("Bay and Islands of San Jorge"), covering 130 square kilometres (50 sq mi), are located on Sonora's northern coast between Caborca and Puerto Peñasco. The islands were first made a federal reserve in 1978 due to its important to migratory birds. They are especially important to species such as the Sterna antillarum, colonies of Sula leucogaster, Myotis vivesi and Zalophus californianus. The islands are large rocks and are white from guano. The beaches extend for ten km and end at the bay of San Jorge on the south end. The area is home to sea lions and a type of bat that fishes. There are sand dunes with arid zone vegetation as well as a small estuary. The climate is very arid and semi hot with an average temperature of between 18 and 22 °C (64 and 72 °F).[95]

The Isla Tiburón is an ecological reserve with about 300 species of plants with desert and marine wildlife. The island was once inhabited by the Seris, and they still consider it their territory.[96]

The La Mesa el Campanero-Arroyo El Reparo reserve is found in the municipality of Yécora. It is a mesa with mountains which cover 43,000 hectares (430 km2; 170 sq mi), containing pine and tropical forests, rivers, arroyos, rock formations and dirt roads. Due to its altitude of between 700 and 2100 masl, its temperatures are temperate for the state. It is part of the Sierra Madre Occidential bio region and in the upper basins of the Yaqui and Mayo rivers.[97]

Politics and government

Sonora is divided into 72 municipalities.