Where Does the Missouri River Begin and End?

Bureau of Land Management/CC-BY 2.0

The Missouri River begins near Three Forks, Montana, and runs until it merges with the Mississippi River near St. Louis, Missouri. The Missouri River stretches out across 2,341 miles.

The Missouri River’s waters come from where the Jefferson, Madison and Gallatin Rivers converge. The river was very prone to flooding when the area first began to be settled by European settlers. These floods were a key part of the ecosystem in the area. Today, the river is impounded by 15 dams along its main route, and the dams have altered flooding and the route of the river. The area referred to as the Missouri Valley is now very populous and does not flood like it did in the past, but these actions have had an affect on water quality and have taken a heavy toll on fish and wildlife.