Where is the Missouri River Located?

The Missouri River is located in the Unites States and is a tributary of the Mississippi River. The Missouri starts at Brower’s Spring, before joining the Madison, Jefferson, and Gallatin rivers in Montana. From this point, it flows through its valley south and east and dumps into the Mississippi River at St. Louis, Missouri. The Missouri is 2, 540 miles and is the longest river in the U.S.