The headwaters of the Pecos River are located north of Pecos, New Mexico

Pecos, New Mexico

Pecos is a village in San Miguel County, New Mexico, United States. The population was 1,441 at the 2000 census, growing much faster than in other parts of San Miguel County, partly because Pecos is within commuting distance of Santa Fe. The village is built along the Pecos River which flows from...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, at an elevation of over 12,000 feet on the western slope of the Sangre de Cristo mountain range

Sangre de Cristo Mountains

The Sangre de Cristo Mountains are the southernmost subrange of the Rocky Mountains. They are located in southern Colorado and northern New Mexico in the United States...

 in Mora County. The river flows for 926 miles (1,490 km) through the eastern portion of that state and neighboring Texas

Texas

Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...

 before it empties into the Rio Grande

Rio Grande

The Rio Grande is a river that flows from southwestern Colorado in the United States to the Gulf of Mexico. Along the way it forms part of the Mexico – United States border. Its length varies as its course changes...

 near Del Rio

Del Rio, Texas

Del Rio is a border city in and the county seat of Val Verde County, Texas, United States.. Del Rio is connected with Ciudad Acuña via the Lake Amistad Dam International Crossing and Del Río-Ciudad Acuña International Bridge...

. The river's drainage basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 is approximately 44300 square miles (114,736.5 km²) in size.
There are multiple dams along the Pecos River.