Eastern Sonora is a mountainous region with a mixed semiarid and subhumid climate. It encompasses the northwestern edge of the Sierra Madre Occidental. The Sonoran Desert dominates the western part of the state, which is covered by low, scattered mountains and wide plains. Despite its aridity, the Sonoran Desert has diverse plant and animal life.

The state's population is clustered around Heroica Nogales (Nogales), at the Arizona border (which is contiguous with the city of Nogales); Hermosillo; Guaymas, a gulf port and deep-sea fishing resort; and Ciudad Obregón, in the Yaqui River valley. Since the 1940s these and other communities have flourished, their hinterlands developed by irrigation projects producing vegetables, cereals, cotton, tobacco, chickpeas, and corn (maize). Major highways and railroads from Mexicali (Baja California state) and Heroica Nogales to Mexico City traverse the state. Airports are situated in the major cities.

Sonora produces nearly all of Mexico's copper and a large proportion of its fish and pork. Since the late 20th century the spread of maquiladoras (maquiladora) (export-oriented assembly plants), spurred by the North American Free Trade Agreement, has boosted the state's output of automobiles and other manufactures. Cross-border traffic has also increased owing to greater exports and migration to the United States; however, there have also been heightened concerns regarding drug trafficking (with attendant violence and corruption) and the risks taken by undocumented migrants attempting to cross the desert.

Explored by Spaniards in the 1530s, Sonora became an important colonial copper-, gold-, and silver-mining district. It became a state in 1830 but lost part of its northern lands to the United States in the Gadsden Purchase of 1853. U.S. filibusterers brought further turmoil in subsequent decades, and the Yaqui Indian peoples fought until the 20th century to retain their independence. During the Mexican Revolution Sonora produced such national leaders as Adolfo de la Huerta (Huerta, Adolfo de la), Alvaro Obregón (Obregón, Álvaro), and Plutarco Elías Calles (Calles, Plutarco Elías).

Sonora's state government is headed by a governor, who is elected to a single term of six years; the representatives in the unicameral legislature, the State Congress, are elected for three-year terms. The state can levy taxes, but in reality it depends on the federal government for most of its revenue. Like other Mexican states, Sonora is divided into local governmental units called municipios (municipalities), each of which may include a city or town and its hinterland or, alternatively, a group of villages.

Several ecological reserves are located in Sonora, including the volcanic and desert region of El Pinacate y Gran Desierto de Altar Biosphere Reserve in the northwest and the Bay and Islands of San Jorge, a bird and marine habitat on the Gulf of California. The San Jorge area is part of a larger region of islands and coastal areas around the gulf collectively designated a UNESCO World Heritage site in 2005. Hermosillo has a museum dedicated to the preservation of Sonoran culture and a state historical museum. Area 70,291 square miles (182,052 square km). Pop. (2000) 2,216,969; (2005) 2,394,861.