The Red River is the most southern of the large tributaries of the Mississippi River, extending 1290 miles. It is generally referred to as Red River from the point where Prairie Dog Town Fork emerges from the Texas Panhandle to join the Oklahoma–Texas border. The main river is approximately 800 miles long. It rises in two branches in the Texas Panhandle and flows southeast between Texas and Oklahoma and between Texas and Arkansas. It then turns south, enters Louisiana, and crosses southeast to the Atchafalaya and the Mississippi rivers. The river is navigable for small ships above Natchitoches.