What is one of the two longest rivers in the United States?

The Missouri River is indeed one of the two longest rivers in the United States. It stretches approximately 2,341 miles from its source in Montana to its confluence with the Mississippi River in St. Louis, Missouri. This makes it the longest river in the U.S., surpassing even the Mississippi River itself when measured from its headwaters to the point where it joins the Mississippi. The length of a river is often significant as it can influence commerce, transportation, agriculture, and ecosystems.

Other rivers mentioned, such as the Ohio River, while significant, do not match the length of the Missouri River. The Nile and Amazon Rivers, although longer than the Missouri, are located in different countries and are not part of the U.S. river system. Therefore, the Missouri River's designation as one of the longest is based on its considerable length and its integral role in the geography and history of the United States.