What is the longest river in the United States?
Quick answer
The Missouri River is the longest river in the United States, at about 2,341 miles (3,767 km), according to the US Geological Survey. The Mississippi is almost the same length, about 2,340 miles. Together, the Missouri–Mississippi system is the fourth-longest river system in the world.
The 5 longest US rivers
| Rank | River | Length (approx.) | Flows through |
|---|---|---|---|
| 1 | Missouri | 2,341 miles | Montana to Missouri |
| 2 | Mississippi | 2,340 miles | Minnesota to the Gulf of Mexico |
| 3 | Yukon | 1,980 miles | Canada and Alaska |
| 4 | Rio Grande | 1,900 miles | Colorado to the Gulf; forms the US–Mexico border |
| 5 | St. Lawrence | 1,900 miles | Shared with Canada |
River lengths vary between sources because rivers change course and measuring methods differ.
Missouri vs Mississippi
| Missouri | Mississippi | |
|---|---|---|
| Source | Rocky Mountains, Montana | Lake Itasca, Minnesota |
| Ends | Joins the Mississippi near St. Louis | Gulf of Mexico, south of New Orleans |
| Nickname | “Big Muddy” | “Father of Waters” |
| Famous for | The Lewis and Clark expedition (1804–1806) | Mark Twain, steamboats, the blues |
The Missouri is longer, but the Mississippi carries more water and is usually considered the “main” river, since the Missouri flows into it.
Which is longest entirely within the US?
Both the Missouri and the Mississippi flow entirely within the United States, so the Missouri wins this title too. Rivers like the Yukon and the Rio Grande cross or form international borders.
Why the Mississippi matters
Its basin drains water from all or part of 31 US states and two Canadian provinces, about 40% of the contiguous US. Barges on the river carry huge amounts of grain, coal and other goods.
Europe’s longest river is the Volga. For the center of the country, see the geographic center of the contiguous US.
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