What is the longest river in the United States?

The Missouri River is recognized as the longest river in the United States, stretching approximately 2,341 miles from its source in the Rocky Mountains of Montana to its confluence with the Mississippi River in St. Louis, Missouri. Its extensive length surpasses that of other well-known rivers in the United States.

The Mississippi River, while one of the most significant and historically important rivers in the country, is about 2,340 miles in length, making it slightly shorter than the Missouri when considering the standard definitions of their lengths. The Yukon River, which flows through Alaska and into Canada, is also not a contender in the context of U.S. rivers solely. Lastly, the Columbia River, which runs between Washington and Oregon, is important for its ecological and economic impact but is significantly shorter than both the Missouri and Mississippi Rivers. Thus, the Missouri River holds the title as the longest river in the United States.