Which river is the longest river in the United States?

The Missouri River is recognized as the longest river in the United States, measuring about 2,341 miles in length. It flows from the Rocky Mountains in Montana and travels through several states, including North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri, before joining the Mississippi River. The significance of the Missouri River extends beyond its length; it has played an essential role in the development and exploration of the American West.

In contrast, while the Mississippi River is often more well-known and is one of the major rivers in North America, it is shorter than the Missouri River at approximately 2,340 miles. The Columbia and Colorado Rivers are also important waterways, but they are not as long as the Missouri River, with the Columbia measuring about 1,243 miles and the Colorado about 1,450 miles. This distinction in length is what makes the Missouri River the correct answer to this question.