city, southern Sonora estado (state), northwestern Mexico. It lies in the heart of the Yaqui Valley, at 330 feet (100 m) above sea level on the coastal plain, near the Yaqui River. The climate is hot and dry. With the completion in the 1950s of irrigation projects on the Yaqui, vast areas of farmlands have been brought under cultivation, and Ciudad Obregón has become an important commercial centre with an airport, cotton gins, granaries, and packing plants. Cotton is the major crop in the area, but wheat, rice, sesame, and corn (maize) are also important. The city houses the Regional Technical Institute of Sonora (1955). It is on the main highways and railroads from Mexicali and Nogales to Mexico City. It was named for the Mexican general and president Álvaro Obregón, who was born in Sonora. Pop. (2000) city, 250,790; (2005 prelim.) urban agglom., 375,800.