Red River, the lowest western branch of the Mississippi, rises near the eastern border of New
Mexico, flows eastward through Texas, forming the entire southern boundary of Indian Territory, thence south-east through Arkansas and Louisiana, and enters the Mississippi below 31° N. lat. It is 1600 miles long, and receives numerous branches, the Washita (Onachita) the most important. It is navigable for seven months to Shreveport (350 miles). A few miles above is the Great Raft, of driftwood, which formerly blocked up the river.