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 Red
River of the North, c.310 mi (500 km) long, formed N of Lake
Traverse, NE S.Dak., by the confluence of the Bois de Sioux and the
Otter Tail rivers. It flows N between Minnesota and North Dakota and
crosses the Canadian border into Manitoba, emptying into Lake
Winnipeg. The river drains the principal spring wheat-growing area of
the United States and Canada : the rich Red River valley region, the
bed of the ancient Lake Agassiz. Its chief tributary is the Assiniboine
River.