Hidalgo (ēħälˈgō) [key], state (1990 pop. 1,888,366), 8,058 sq mi (20,870 sq km), central Mexico. Pachuca de Soto is the capital. Crossed by the Sierra Madre Oriental, the state is extremely mountainous; in the southern and western areas, however, are plains and fertile valleys lying within Mexico's central plateau. The climate is warm in the lower valleys, temperate on the plateau, and cold in the mountains. One of Hidalgo's chief crops is maguey (see amaryllis), grown on the central plateau. Alfalfa, corn, sugarcane, and coffee are also cultivated. The state's main industry is mining (particularly around Pachuca), and Hidalgo is a leading national producer of silver, gold, copper, lead, iron, and sulfur. Cement, textile, automobile manufacturing and especially oil refining are other major industries. The territory was occupied successively by the Toltec (whose capital was Tollán—now Tula), the Chichimecs, and the Aztecs. Conquered by the Spanish in 1530, it was part of the province and state of Mexico until it became the separate state of Hidalgo in 1869. There are several hot springs in Hidalgo.