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.
See more at Wikipedia.org...

Noun
1. the longest river in the United States; arises in Montana and flows southeastward to become a tributary of the Mississippi at Saint Louis
(synonym) Missouri
(hypernym) river
(part-holonym) United States, United States of America, America, US, U.S., USA, U.S.A.