8 Missouri River Facts That Will Blow Your Mind

Missouri River Colors
© Brian O'Kelly/iStock via Getty Images

Written by Katie Downey

Published: February 17, 2024

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The Missouri River is one of the longest and most interesting rivers in the U.S. Missouri is only one of the states this river crosses. In this article, we will discover how the river was named, where it starts and ends, and so much more. Be sure to follow the links to some other interesting Missouri River articles. Now, let’s dive into some of the best Missouri River facts that will blow your mind!

8. The Missouri River is the Longest River in North America

MAY 23 2019, USA - THREE FORKS, MT - Missouri River Breaks National Monument, the source of the Missouri River, comprised of Jefferson, Madison and Gallatin Rivers

The Missouri River is the fourth longest river in the world once it merges with the Mississippi River.

©Joseph Sohm/Shutterstock.com

The U.S. has plenty of extremely long rivers, such as the Mississippi, Yukon, Rio Grande, Arkansas, and Colorado Rivers. Surprisingly, the Missouri River takes first place as the longest river in the U.S. and in all of North America. In fact, it is such a massive river that it enters numerous national parks and crosses through everything in the U.S., from swamps to deserts. The Missouri River has a length of 2,341 miles before it connects with the Mississippi River. To put that distance into perspective, the U.S. is 2,742 miles from east to west coast.

7. The Missouri River Meanders through Seven States

Mississippi and Missouri Rivers on vintage 1920s map (printed in 1926 - copyrights expired) with a red pushpin on St Louis, selective focus

This 1920s map shows the Mississippi and Missouri Rivers, where they meet.


The Missouri River is super long, but did you know it passes through a total of seven states? That’s a lot, even for a long river! The Missouri and Mississippi Rivers come together and create the fourth longest river system in the world at 3,979 miles long. Before that happens, the river begins at an elevation of 4,045 feet on the eastern slope of the Rocky Mountains as a confluence of the Jefferson, Madison, and Gallatin rivers near Three Forks, Montana, to its meeting place with the Mississippi River in St. Louis, Missouri. The states the river flows through are Montana, North Dakota, South Dakota, Nebraska, Iowa, Kansas, and Missouri.

6. Humans have Drastically Changed the Flow of the Missouri River

Lake Sharpe South Dakota

Humans have tampered with the river’s flow for more than a century.

©Harry Weddington, U.S. Army Corps of Engineers / This image or file is a work of a U.S. Army Corps of Engineers soldier or employee, taken or made as part of that person’s official duties. As a work of the U.S. federal government, the image is in the public domain. – Original

The Missouri River was once as wild and free as the Yellowstone River until humans began to dictate what the massive river did. Since then, six major dams have maintained the river. Those dams are the Fort Peck, Garrison, Oahe, Big Bend, Fort Randall, and Gavin’s Point. The six main dams were built in order to store water for hydroelectric power generation, maintain agriculture irrigation, and for recreational uses within reservoirs.

5. The Diversity of the Wildlife on the Missouri River is Exceptional

An american bald eagle flies off with a fish on Coeur d'Alene Lake in Idaho.

Some species found in and along the Missouri River are endangered or protected.

©Gregory Johnston/Shutterstock.com

Many types of mammals, aquatic life, amphibians, reptiles, birds, and insects lay claim to the extensive landscape the Missouri River passes through. Near the beginning of the river are grizzly bears, wolves, eagles, elk, prairie dogs, bighorn sheep, bison, osprey, longhorn, and many others. In fact, 60 species of mammals, 301 species of birds, and 52 species of reptiles and amphibians exist along the river! Several bats, birds, and fish are protected under the Endangered Species Act.

4. The Missouri River is Also Called “Big Muddy”

MAY 17 2019, HERMANN MISSOURI USA - The Hermann Bridge was a cantilevered truss bridge over the Missouri River at Hermann, Missouri between Gasconade and Montgomery County

The Missouri River has earned several nicknames over the years.


One of the most commonly used nicknames of the Missouri River is “Big Muddy.” The nickname came from the fact that the once clear water of a mountain stream picks up so much sediment as it travels away from its source. The sedimentation is what gives the river its muddy look. The Mississippi is also sediment-heavy, but once the two merge, it should be known as the biggest muddy river.

3. Lewis and Clark Expedition Travelled the Missouri River

Lewis and Clark Expedition

The Lewis and Clark Expedition paved the way for pioneers and mountain people throughout the West and Midwest.

©Charles Marion Russell / Public domain – Original / License

From May 24 through June 13, 1805, Lewis and Clark spent three weeks exploring the segment that is now the Upper Missouri National Wild and Scenic River, which is referred to as the Missouri Breaks. That area has been protected since the 1970s by the federal government, focusing on the National Wild and Scenic River regulation.

2. The Missouri River Passes Through Several Natural Wonders

Badlands National Park

Badlands National Park is a work of art through which the Missouri River passes.


What is now called the Upper Missouri River Breaks National Monument was once a flat land. The land had been laid down over time in layers, starting with the sediment and coast of the massive inland sea that once covered the Great Plains. Volcanic activity created an intense change in the topography of the flat land. It caused it to fold, fault, and then uplift into tall peaks, which would also be sculpted by glaciers. Finally, erosion occurred over millions of years and formed what is now called “the Breaks.” This is a favorite among kayakers.

The river also wraps through the canyons, amazing stone sculptures of the Badlands of South Dakota, and numerous parks. There is even an area specific to prairie dog watching.

1. The Name of the Missouri River Came From an Indigenous Tribe

Bodmer Missouria Otoe Ponca Indians

The first tribes of the Sioux Native Americans named the Missouri River.

©Karl Bodmerderivative work Uyvsdi / Public domain – Original / License

Native American tribes such as the Blackfeet, Hidatsa, Ottoe, Missouria, and Crow lived in the northern region where the Missouri River began. From the Siouan language, the name they gave the river was “Ouemessorita,” which means “people of the wooden canoe.” Later, it was anglicized to be spelled and pronounced Missouri.

French explorers Father Jacques Marquette and Louis Jolliet, in May 1673, called the river “Pekitanoui,” which was from the Algonquian/Peoria Indian language and meant Muddy Water.

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About the Author

Katie Downey is a writer for A-Z Animals where her primary focus is on wildlife, arachnids and insects. Katie has been writing and researching animals for more than a decade. Katie worked in animal rescue and rehabilitation with handicapped cats and farm animals for many years. As a resident of North Carolina, Katie enjoys exploring nature with her son, educating others on the positive role that insects and spiders play in the ecosystem and raising jumping spiders.

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