Missouri River

The Missouri River is a tributary of the Mississippi River in the United States. The Missouri begins at the confluence of the Madison, Jefferson, and Gallatin rivers in Montana, and flows into the Mississippi north of St. Louis, Missouri. At 2,341 mi (3,767 km) in length, it drains about one-sixth of the North American continent.

The Missouri in its original natural meandering state was the longest river in North America. Nearly 72 miles of the river has been cut off in channeling and so it is now comparable in length to the Mississippi River. The combination of the two longest rivers in North America forms the third longest river in the world.

At its confluence, the Missouri nearly doubles the volume of the Mississippi, accounting for 45 percent of the flow at St. Louis in normal times and as much as 70 percent of the flow during some droughts.

The river is nicknamed "Big Muddy" and also "Dark River" because of the high silt content. The river meanders from bluff to bluff in the flat Midwestern states, leading to the nickname the "Wide Missouri."