Guanajuato (gwänähwäˈtō) [key], state (1990 pop. 3,982,593), 11,805 sq mi (30,575 sq km), W central Mexico, on the central plateau. The city of Guanajuato is the capital. The state's high average elevation (6,000 ft/1,829 m) provides a moderately cool, healthful climate. Guanajuato is crossed in the north by transverse ranges of the Sierra Madre Occidental, some of which reach heights of 11,000 ft (3,353 m). In the south are fertile plains supporting stock raising and the cultivation of wheat, corn, other grain crops, and beans. The Lerma and its tributaries form the chief river system.
Despite the steadily growing importance of agriculture, Guanajuato is noted primarily as Mexico's foremost mining state; much silver and gold is extracted, and mercury, lead, tin, copper, fluorite, and opals are also produced. Industrial products from the cities—Guanajuato, Celaya, León, and Irapuato—include textiles, saddles and other leather goods, and foodstuffs. Oil refining is also a significant part of the economy.
Joined with Querétaro de Arteaga, the state was a Spanish intendancy until 1824. A leading silver producer of Spanish America, Guanajuato declined in economic importance during the wars of the 19th cent. There has been significant outmigration from the state to the United States in recent years.