The longest river in North America is the Missouri River. Stretching approximately 2,341 miles, it flows through several states, including Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri, before merging with the Mississippi River near St. Louis. Historically significant, the Missouri River was vital for Native American tribes and later for European explorers and settlers. Today, it serves crucial purposes such as irrigation, transportation, and recreational activities, while also supporting diverse ecosystems along its banks.