About 2,341 miles · 7 states · source Three Forks, MT · mouth near St. Louis
Missouri River map
The Missouri is the longest river in the United States, running about 2,341 miles from Three Forks, Montana, to the Mississippi just above St. Louis. It crosses or borders seven states.
Where the Missouri is
The Missouri begins at Three Forks, Montana, where the Jefferson, Madison and Gallatin rivers meet at about 4,045 ft. It flows north and east past Great Falls, bends southeast through the Dakotas, then runs along the eastern edge of Nebraska and across Missouri to join the Mississippi about 15 miles above St. Louis. At about 2,341 miles it is a few miles longer than the Mississippi; together they drain about a sixth of the continent.
States along the river
- Montana — source, Great Falls and Fort Peck Dam.
- North Dakota — Lake Sakakawea, Bismarck and Mandan.
- South Dakota — Lake Oahe, Pierre (the capital sits on the bank), and a short stretch of the Nebraska border.
- Nebraska — the entire eastern border, with Omaha.
- Iowa — the entire western border, with Sioux City and Council Bluffs.
- Kansas — the northeastern border from Kansas City up to the Nebraska line.
- Missouri — across the state from Kansas City to St. Louis, through Jefferson City.
The river is a state border for about 500 miles: Nebraska–South Dakota, Nebraska–Iowa, Nebraska–Missouri and Kansas–Missouri. Its drainage basin also takes in parts of Wyoming, Colorado and Minnesota.
Key measurements
- Length: about 2,341 miles, the longest in the country.
- Basin: about 530,000 square miles, the largest of any US tributary.
- Main tributaries: the Yellowstone (joins near the Montana–North Dakota line), the Platte (joins below Omaha), the Kansas (joins at Kansas City) and the Osage.
- Six mainstem dams built by the Army Corps of Engineers between 1933 and 1964: Fort Peck, Garrison, Oahe, Big Bend, Fort Randall and Gavins Point. Lake Oahe and Lake Sakakawea are each more than 200 miles long.
Cities on the river
Two state capitals sit directly on the Missouri: Bismarck, North Dakota, and Pierre, South Dakota; a third, Jefferson City, Missouri, is on the lower river. Omaha is the largest city on the river, followed by Kansas City, which grew up at the mouth of the Kansas River. Great Falls, Montana, is named for a series of five falls that stopped Lewis and Clark for a month in 1805.
How the river shaped the map
Lewis and Clark followed the Missouri west in 1804–1805, and the river became the highway into the Louisiana Purchase. Its lower course was fixed as the Kansas–Missouri and Nebraska–Iowa lines when those states were created, which is why Nebraska has one crooked eastern edge and three straight ones. Like the Mississippi, the river has shifted since; Carter Lake, Iowa, is stranded on the Nebraska bank by an 1877 flood.
Related maps
- Mississippi River — the river it joins.
- Great Plains — the region it crosses.
- Yellowstone — source of its largest tributary.
- Longest US rivers · All geography maps.