The ten longest rivers in the United States as measured by the United States Geological Survey.
These are the ten longest rivers in the United States as measured by the USGS. Most people would guess that the Mississippi River is the longest river in the United States but that is not the case.
Other sources may list the Mississippi as the longest river in the country because they are counting the tributaries of the Mississippi as well. The USGS considers each river separate so the longest river in the country is actually a tributary of the Mississippi River.
Ten Longest Rivers in the United States
1. Missouri River - 2,540 miles
Image Source (Missouri River in Montana)
As stated above some sources consider the Missouri River a part of the Mississippi River and include its length combined with the Mississippi. The USGS lists the Missouri River as a separate river and therefore it is the longest river in the United States at 2,540 miles. The Missouri River starts in the Rocky Mountains in Montana and flows into the Mississippi River near St. Louis, Missouri.
2. Mississippi River - 2,340 miles
Image Source by Shannon
The Mississippi River begins at Lake Itasca in Northwestern Minnesota and flows 2,340 miles to where it flows into the Gulf of Mexico in southern Louisiana. Though not the longest river in the United States the Mississippi has the largest drainage area in the country and one of the largest drainage areas in the world. Personally I think it's a great thrill to drive over the mighty Mississippi every time I do it.
3. Yukon River - 1,980 miles
The Yukon River begins at Llewellyn Glacier at Atlin Lake in northwestern British Columbia and flows 1,980 miles through the Yukon Territory and into Alaska where it eventually flows into the Bering Sea. I've camped along the Yukon River and driven over it numerous times and it has a greenish tint to it due to the high mineral content in the water.
T-4. Rio Grande - 1,900 miles
The Rio Grande begins at the base of Canby Mountain in Colorado and flows 1,900 miles to where it flows into the Gulf of Mexico just south of Brownsville, Texas and north of Matamoros, Mexico. I've driven along parts of the Rio Grande along the Texas-Mexico border and would not call it a large or grand river in many areas.
T-4. St. Lawrence River - 1,900 miles
The St. Lawrence River begins at the end of Lake Ontario between Kingston, Ontario in Canada and Cape Vincent, New York in the United States. From there the river flows through the Thousand Islands and travels 1,900 miles to where it empties into the Gulf of St. Lawrence and the Atlantic Ocean. I've traveled extensively along the St. Lawrence River and visited the St. Lawrence Seaway canals and locks as a kid. The river becomes massively wide north of Quebec City.
6. Arkansas River - 1,460 miles
The Arkansas River begins in the Rocky Mountains in Colorado near Leadville. It then flows 1,460 miles to where it merges with the Mississippi River in southeastern Arkansas near the ghost town of Napoleon.
7. Colorado River - 1,450 miles
Image Source by Christian Mehlführer
The Colorado River begins at La Poudre Pass Lake in beautiful Rocky Mountain National Park in northern Colorado and ends where it flows into the Gulf of California between Baja California and Sonora in Mexico. Of course the Colorado River is most famous for carving and flowing through the magnificent Grand Canyon. I've hiked to and crossed over the foot bridges that go over the Colorado River at the bottom of the Grand Canyon a number of times.
8. Atchafalaya River - 1,420 miles
The Atchafalaya River begins in Curry County New Mexico and flows 1,420 miles through Texas and Louisiana south of the Mississippi River and empties into the Gulf of Mexico at Atchafalaya Bay.
9. Ohio River - 1,310 miles
The Ohio River forms when the Allegheny and Monongahela Rivers merge at Point State Park which is in Pittsburgh, Pennsylvania. From there the Ohio River flows 1,310 miles until it merges into the Mississippi River near Cairo, Illinois.
10. Red River - 1,290 miles
Image Source by Henley Quadling
The Red River begins in two forks which start in Texas and Oklahoma. The Texas fork is called the Prairie Dog Town Fork while the Oklahoma Fork is called Buck Creek and then North Fork. Once the forks merge the Red River flows 1,290 miles until it flows into both the Atchafalaya and Mississippi Rivers in Louisiana.
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