The Missouri River is part of the Mississippi River System and drains the Rocky Mountains.

The Missouri River, one of the longest rivers in North America, is a major tributary of the Mississippi River. It drains the Rocky Mountains and flows through the central United States, joining the Mississippi River near St. Louis. The river plays a critical role in transportation, agriculture, and water supply, shaping the landscape and economy of the regions it passes through. It is a key component of the larger Mississippi River System.