<P> The Red River, or sometimes the Red River of the South, is a major river in the southern United States of America . Ir was named for the red - bed country of its watershed . It is one of several rivers with that name . Although it was once a tributary of the Mississippi River, the Red River is now a tributary of the Atchafalaya River, a distributary of the Mississippi that flows separately into the Gulf of Mexico . It is connected to the Mississippi River by the Old River Control Structure . </P> <P> The south bank of the Red River formed part of the US--Mexico border from the Adams--Onís Treaty (in force 1821) until the Texas Annexation and the Treaty of Guadalupe Hidalgo . </P> <P> The Red River is the second - largest river basin in the southern Great Plains . It rises in two branches in the Texas Panhandle and flows east, where it acts as the border between the states of Texas and Oklahoma . It forms a short border between Texas and Arkansas before entering Arkansas, turning south near Fulton, Arkansas, and flowing into Louisiana, where it flows into the Atchafalaya River . The total length of the river is 1,360 miles (2,190 km), with a mean flow of over 57,000 cubic feet per second (1,600 m / s) at the mouth . </P> <P> The Red River rises near the edge of the northwestern dip slope of the Llano Estacado mesa in two forks in northern Texas and southwestern Oklahoma . The North Fork Red River meets the southern and largest fork near the Texas--Oklahoma border . The southern fork, which is about 120 miles (190 km) long, is generally called the Prairie Dog Town Fork . It is formed in Randall County, Texas, near the county seat of Canyon, by the confluence of intermittent Palo Duro Creek and Tierra Blanca Creek . </P>

Where does the red river in texas start