The longest river in North America is the Missouri River. Stretching approximately 2,341 miles (3,767 kilometers), it flows through several U.S. states, including Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri, before joining the Mississippi River near St. Louis, Missouri. The Missouri River played a crucial role in the exploration and settlement of the American West and served as a vital transportation route for goods and people. It is also important for agriculture, providing water for irrigation and supporting diverse ecosystems along its banks.