Red River
the lowest W. branch of the Mississippi, rises near the E. border of New Mexico, flows E. through Texas, forms what was the S. boundary of Indian Territory, thence S. E. through Arkansas and Louisiana, and enters the Mississippi below lat. 31° N. It is 1,600 miles long, and receives numerous branches, the Washita the most important. t. It is navigable for seven months to Shreveport (350 miles).