The Brazos River, called the Río de los Brazos de Dios by early Spanish explorers, is the 14th-longest river in the United States at 1,280 miles (2,060 km) from its headwater source at the head of Blackwater Draw, Roosevelt County, New Mexico to its mouth at the Gulf of Mexico with a 45,000-square-mile (116,000 km2) drainage basin. Being one of Texas' largest rivers, it is sometimes used to mark the boundary between East Texas and West Texas.

Blackwater Draw is an intermittent stream channel about 140 km (87 mi) long, with headwaters in Roosevelt County, New Mexico, about 18 km (11 mi) southwest of Clovis, New Mexico, and flows southeastward across the Llano Estacado toward the city of Lubbock, Texas, where it joins Yellow House Draw to form Yellow House Canyon at the head of the North Fork Double Mountain Fork Brazos River. It stretches across eastern Roosevelt County, New Mexico, and Bailey, Lamb, Hale, and Lubbock Counties of West Texas and drains an area of 1,560 sq mi (4,040 km2).