Where Does the Missouri River Start?

© iStock.com/Matthew Howieson

Written by Jennifer Gaeng

Updated: July 20, 2023

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Infographic about the Missouri River
The Missouri River is longer than the Mississippi River, which it joins in St. Louis.

Today we’re going to be learning about the longest river in America, the Missouri River! Research suggests that the Missouri river formed nearly 30 million years ago! However, its most recent change in course happened about 115,000 years ago. The water flow of the Missouri River is regulated by the U.S. army corps of engineers. This once free-flowing river has since been channelized in its lower regions. It has also been impounded in its northern regions by at least six dams. So, where exactly does this historical river start? Let’s find out!

Where Exactly Does the Missouri River Start?

The Missouri River starts in the Rocky Mountains.


The Missouri River starts in the Rocky Mountains at Three Forks, Montana. It flows 2,342 miles across the United States, stopping in Missouri. It drains 1/6 of the United States and flows east and south. This fascinating river covers roughly 500,000 square miles and crosses through 10 American states and two Canadian provinces.

How Deep Is the Missouri River?

Missouri River has an average depth of 10 to 20 feet.

©iStock.com/Matthew Howieson

The average depth of the Missouri River channel is about 10-20 feet, depending on the area. It is said that some of its deeper parts can range anywhere from 120 ft to 150 ft. However, this river meets and merges with another river that creates one of the biggest flowing systems in the world. It is said at this point that the depth can reach nearly 200 ft!

Even though the average depth of this water is not very deep, this is because there is a vast amount of sand and water-soaked gravel beneath the surface. The varying levels of sandbars, rocks, holes, and fast-moving currents make it unsafe for people to swim in the Missouri River. Even paddlers must remain cautious because the depth of this river varies so often.

What States Does the Missouri River Run Through?

The Missouri River runs through 7 different US states and two Canadian provinces. Starting in Montana, its 2,342 mi journey then flows through:

  • Iowa
  • Kansas
  • Missouri
  • Nebraska
  • North Dakota
  • South Dakota.

In Canada, the Missouri River runs through Alberta and Saskatchewan.

Does the Missouri River Intersect With Another River?

The Mississippi River joins the Missouri River at St Louis.


The Missouri River intersects with the Mississippi River roughly 20 miles north of St Louis, Missouri. It flows southeast from Montana to Missouri. The Mississippi River starts in Minnesota and runs all the way down the Midwest until it meets the Missouri River in the state of Missouri. Here, both rivers merge and then flow through Arkansas, Tennessee, Mississippi, and Louisiana. The mouth then opens into the Gulf of Mexico, about a hundred miles south of New Orleans!

Where Is the Missouri River Located on a Map?

The Missouri River begins in Montana and runs 2,341 miles to St. Louis, Missouri, where it meets the Mississippi River. Major cities along the river include: Great Falls in Montana, North Dakota’s capital city Bismarck, South Dakota’s capital Pierre, Sioux City and Council Bluffs in Iowa, Omaha in Nebraska, Kansas City — Kansas and Missouri, and Saint Joseph, Jefferson City (Missouri’s capital), and Saint Charles in Missouri.

Where Does the Missouri River Rank on a Global Scale?

The Missouri river is the fourth largest in the world when combined with the Mississippi and possessing a total length of 3,710 miles. It follows the Yangtze which is 3,964 miles and the third-largest, while the Amazon comes second at 4,000 miles. First position goes to the Nile with a length of 4,160 miles.

What Animals Live on the Missouri River?

what do bluegill eat

Bluegill is in abundance in the Missouri River.


The Missouri River is home to more than 25 distinct species of wildlife! You can find many diverse types of fish and amphibians. This river is also a pathway for many different species of birds, most importantly the American bald eagle! You can even find more than 12 different types of snakes and turtles along the river. Large mammals such as foxes, black bears, grizzly bears, and coyotes call the Missouri River home. It also hosts many different species of small mammals such as mice, squirrels, and prairie dogs!

Not only has the Missouri River been used for traveling, water usage, and drainage for many years, but it has also been used for hunting and fishing. This river is a habitat for many varied species of fish, the most popular being the bluegill, crappie, trout, and catfish. On rare occasions, bull sharks have swum from the Gulf of Mexico, up the Mississippi through the Missouri River. They have even been found in St Louis, Missouri, a landlocked state where sharks are non-existent!

What Is the Missouri River’s History?

Inside the walls of Fort Union Trading Post, the dominant fur trading post on the Upper Missouri River, North Dakota.


The Missouri River is not just home to many unusual species of wildlife, it is also filled with rich history! Before many European settlers came to America, native American tribes traveled and formed all along the Missouri River. However, it became notorious long after English settlers and other European settlers came to North America.

It was when Thomas Jefferson was elected as president in 1800 that the Missouri River would then become a key component in expanding the United States further west. When the Lewis and Clark expedition began in 1804, two men traveled throughout the Missouri River. They went from St Louis all the way up until they discovered the Pacific Northwest. This inevitably led up to the Louisiana purchase and expanded the United States by 828,000 square miles!

In Conclusion

The Missouri River may be the longest-running river in America, but it is also the river that has the most vivid backstory. After all, it is the river that separated the English colonies from the Westlands previously owned by the French. It allowed settlers to expand the country to several different states. This river has been used as a source of water, food, and drainage for centuries, long before humans. It is one of the most viable and important rivers in North America and continues to fascinate people to this day!

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About the Author

Jennifer Gaeng is a writer at A-Z-Animals focused on animals, lakes, and fishing. With over 15 years of collective experience in writing and researching, Jennifer has honed her skills in various niches, including nature, animals, family care, and self-care. Hailing from Missouri, Jennifer finds inspiration in spending quality time with her loved ones. Her creative spirit extends beyond her writing endeavors, as she finds joy in the art of drawing and immersing herself in the beauty of nature.

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