Valencia, county, central New Mexico, U.S., in the Mexican Highland section of the Basin and Range Province. The Manzano Mountains lie at its eastern border, and mesas rise in the west. Between mountains and mesas are the southward-flowing Rio Puerco and the Rio Grande. The Isleta (Pueblo) Indian Reservation is in the north, and other areas of interest are Cibola National Forest, Manzano Mountain Wilderness, and Senator Willie M. Chavez State Park.
Pueblo Indians settled in the Rio Grande valley about 1500 and created productive farmland with irrigation. The Spanish arrived with Francisco Vázquez de Coronado’s 1540 expedition. In the next century, Spanish settlers followed El Camino Real to the region and began farming it. Several of Valencia county’s towns date from the late 17th and early 18th centuries. Valencia county was established by Mexico in 1844 and was confirmed as part of the New Mexico Territory in 1852.
Most residents of Valencia county live in the Rio Grande valley. Though agriculture (cattle, milk) persists there, construction, health care, the Santa Fe railroad yards at Belen, and government employment are among the leading elements in the economy. Many residents commute to work in nearby Albuquerque. The county seat is Los Lunas, and Belen is the largest town. Area 1,068 square miles (2,765 square km). Pop.(1990) 45,235.