What is the longest river in the United States?
The Missouri River is the longest river in the United States, at about 3,770 kilometers. It joins the Mississippi River near St. Louis, Missouri.
The Missouri begins in the Rocky Mountains of Montana and flows east and south through the Great Plains. It passes through or along seven states before meeting the Mississippi just north of St. Louis. Explorers Meriwether Lewis and William Clark traveled up the Missouri in 1804 on their expedition to the Pacific.
The Mississippi River is about 3,730 kilometers long, slightly shorter than the Missouri. Together, the Missouri and Mississippi form a river system about 6,000 kilometers long, one of the longest in the world. Their basin drains water from all or part of 31 US states and two Canadian provinces.
America's great rivers
Other long US rivers include the Yukon in Alaska, the Rio Grande, which forms part of the border with Mexico, and the Colorado, which carved the Grand Canyon. River lengths vary slightly between sources because rivers change course and are measured differently.
Did You Know?
The Missouri River is nicknamed the Big Muddy because it carries large amounts of silt.