The longest river in North America is the Missouri River. Stretching about 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. The Missouri River has played a crucial role in the region's history, serving as an important transportation route for Native Americans and European explorers. Its watershed supports diverse ecosystems and communities, contributing to the agricultural and economic landscape of the area.