Red River, so named because of the red-colored sediment it carries, forms much of the boundary between Oklahoma and Texas. It is about 1,300 miles (2,090 kilometers) long. Its drainage basin covers about 90,000 square miles (230,000 square kilometers). The Red River rises in northern Texas. Its north fork has its source east of Amarillo, Texas, and the Prairie Dog Town fork rises south of it. The river flows through southwestern Arkansas and into Louisiana. It joins the Atchafalaya River about 5 miles (8 kilometers) north of Simmesport, Louisiana. See also Lake Texoma .
