Red River. 1 River, 1,222 mi (1,967 km) long, southernmost of the large tributaries of the Mississippi River. It rises in two branches in the Texas Panhandle and flows SE between Texas and Oklahoma and between Texas and Arkansas to Fulton, Ark. It then turns southward, enters Louisiana, and crosses SE to the Atchafalaya and the Mississippi rivers. In Texas it flows rapidly through a canyon in semiarid plains, but later in its course it waters rich red-clay farm lands (whence the name Red). Dams on the river include the Denison Dam (completed 1943), which impounds Lake Texoma, one of the largest reservoirs in the United States. For many years navigation was difficult on the lower course of the Red River due to fallen trees that floated downstream and collected behind obstructions, forming rafts. The Great Raft, a 160-mi (257-km) log-jam built through the centuries, was cleared from the river in the mid-1800s. The river is now navigable for small ships to above Natchitoches, La. There are many lakes along the lower part of the river, and reservoirs serve as flood-control units on its tributaries.
2 River, often called the