The Pecos River rises in northern New Mexico and flows for 926 mi (1,480 km) near the Truchas peaks before it empties into the Rio Grande in Texas. The river drains approximately 38,300 sq mi of territory.

The river is dammed at Alamogordo, Avalon, and McMillan to help irrigate about 25,000 acres (10,120 hectares) as part of the Carlsbad reclamation project (established in 1906). Texas has also dammed the river at the Red Bluff Dam in the western part of that state. New Mexico and Texas disputed water rights to the river until the federal government settled the dispute in 1949.

At the turn of the century, "West of the Pecos" reffered to the rugged "Wild West" of Texas.