Which geographic feature is identified as 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. It flows primarily through the central United States, starting in Montana and eventually merging with the Mississippi River in St. Louis, Missouri. Its significant length and the extensive watershed it drains make it a prominent geographic feature of the U.S.

In contrast, the other rivers listed, such as the Amazon, Nile, and Ganges, while they are among the longest rivers globally, do not pertain specifically to the United States. The Amazon River is in South America, the Nile in northeastern Africa, and the Ganges in India and Bangladesh, thus highlighting the geographical scope of the question.