What Is the Longest River in North America?

By Staff WriterLast Updated Mar 29, 2020 9:47:05 PM ET
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Running between the state of Missouri and its source in Montana, the longest river in North America is the Missouri River. The river flows 2,341 miles until it reaches its mouth at the Mississippi River north of St. Louis. The Missouri River, just slightly longer than the Mississippi River, combines with it to form the fourth largest river system in the world after the Nile, Amazon and Yangtze rivers.