city, capital of Hidalgo estado (state), east-central Mexico. It lies about 50 miles (80 km) northeast of Mexico City in a rich mining district in the Sierra Madre Oriental, 7,959 feet (2,426 metres) above sea level. The district was important to the ancient Toltec culture, and silver mines are said to have been worked in the area in pre-Columbian times. The Spanish founded the city—one of the first settlements in New Spain (New Spain, Viceroyalty of)—in 1534 and took over the mines. The Real del Monte mine, begun in 1739 and still in operation, is one of the most extensive mining properties in the world. The patio (patio process), or Mexican, process of separating silver from the ore by amalgamation with mercury was perfected in Pachuca by Bartolomé de Medina (Medina, Bartolomé de) in the 16th century, and the Pachuca tank used in the cyanide process was developed there in the 20th century.

Light manufacturing and services constitute a growing proportion of the economy, but smelting and metallic-ore reduction are still important. Pachuca has a school of mines and metallurgy (founded 1877) and the Autonomous University of Hidalgo (founded 1869 as the Scientific and Literary Institution; present status, 1961). The ruins of Tula, the Toltec capital, are about 35 miles (55 km) west of Pachuca. Pop. (2000) 231,602.