León, city (1990 pop. 758,270), Guanajuato state, central Mexico. It is located in a fertile river valley c.5,600 ft (1,700 m) high, but with a mild, temperate climate. Frequent floods, which in 1888 almost washed the city away, necessitated the building of a protective dam. León, on the main rail line between El Paso, Tex., and Mexico City, is a commercial, agricultural, and mining center and one of Mexico's leading shoe manufacturers. The city's mines yield gold, copper, silver, lead, and tin. León was officially founded in 1577.