|Countries||United States, Canada|
|- location||Rocky Mountains, Montana|
|- elevation||9,030 ft (2,750 m)|
|- elevation||404 ft (123 m)|
|Length||2,341 mi (3,767 km)|
|Basin size||529,350 sq mi (1,371,000 km2)|
|- average||87,520 cu ft/s (2,478 m3/s)|
The source of the Missouri River is in the Rocky Mountains, in the state of Montana. The Missouri flows eastward, across Montana, south of the border with Canada. It enters the state of North Dakota and then it turns south. It flows through South Dakota. Then it flows past Iowa, Nebraska, Missouri, and Kansas.
Near the city of Kansas City, Missouri, the Missouri turns eastward into the state of Missouri. It flows eastward across the state of Missouri. It joins the Mississippi just north of the city of Saint Louis, Missouri.
The Missouri was very important for the Native Americans who lived on the Great Plains. It was also very important in the history of the United States. The Missouri was used as the route of the Lewis and Clark Expedition in 1804-1806. In the 19th century, the Missouri was very important in the North American fur trade and for transportation of army troops and supplies as well as general transportation and trade as the West was settled.
The nickname of the Missouri is "Big Muddy", because it has a lot of silt.