What’s the Largest Man-Made Lake in Montana

Written by Abdulmumin Akinde
Updated: June 2, 2023
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Montana is the fourth largest state and the 44th most populated state in the United States of America. The state shares a border with South Dakota, Wyoming, Idaho, and North Dakota. Montana is so mountainous that its name originates from the Spanish word for mountain. The state boasts of vast deposits of natural and mineral resources, but these are not the only reason people call it the Treasure State. For those who enjoy the outdoors and the water, Montana also prides itself on its several water bodies, including Fort Peck Lake, the largest man-made lake in Montana. Read on to discover all you need to know about this lake, including its location, size, and the animals that live in it.

Location and Size of the Largest Man-Made Lake in Montana

Fort Peck Lake in Montana - Largest Man-Made Lake in Montana 2
With a surface area of 245,000 acres, Fort Peck Lake is the fifth-largest man-made lake in the United States. It’s the largest reservoir in Montana.

©Beets Productions/Shutterstock.com

Fort Peck Lake is located in the Charles M. Russell Wildlife Refuge in the small town of Fort Peck. The construction of the Fort Peck Dam, the world’s largest earth-filled dam, created the lake.

With a surface area of 245,000 acres, this lake is the fifth-largest man-made reservoir in the United States. Fort Peck Lake is approximately 134 miles long with 1,520 miles of shoreline. It has a maximum depth of about 220 feet. Despite its huge shoreline, the lake is completely secluded, with very few visitors. This is because it is located on the Missouri River in one of Montana’s most remote places. It is roughly 140 miles east of Great Falls and 120 miles north of Billings. The Missouri River, Musselshell River, Fourchette Creek, Timber Creek, Hell Creek, and Dry Creek all flow into the reservoir.

The Fort Peck Marina is located close to the west side of the dam. It provides direct access to the reservoir. The Fort Peck Dam, which is 250.5 feet tall and 21,026 feet long, keeps the water in the reservoir at bay.

The Fort Peck Lake and Dam are part of the vast Charles M. Russell Wildlife Refuge. It is the second-biggest national wildlife refuge in the United States and the largest in Montana. The refuge has paleontological significance because it is the site of some interesting fossil discoveries. In 1988, scientists found fossils of a reasonably complete Tyrannosaurus rex (Devil Rex) in this refuge. Late in 2000, paleontologists unearthed a 70 million-year-old Tyrannosaurus rex specimen known as “B-Rex.” The fossils in each instance were in good condition, with pieces of soft tissue preserved.

Where is the Largest Man-Made Lake in Montana Located on a Map?

The largest man-made lake in Montana is Fort Peck Lake – located in the Charles M. Russell Wildlife Refuge in the small town of Fort Peck. Fort Peck Lake is roughly 140 miles east of Great Falls and 120 miles north of Billings.

History of the Largest Man-Made Lake in Montana 

The area where Fort Peck Lake is currently located was once occupied by native tribes like the Sioux, Crow, Assiniboine, and Blackfeet people. The Corps of Discovery Expedition led by Captain Meriwether Lewis and Lieutenant William Clark explored the area for the first time in 1804. 

During their initial exploration of Fort Peck, Lewis and Clark were astounded by the area’s purely natural surroundings, particularly the section of the Missouri River in that location. The Missouri River was the main means of travel in and out of Montana and other small settlements surrounding it. Commercial activities in this region were built around the river and the access it provided. Due to repeated flooding, ships ceased using the lower Missouri River between the 1880s and 1903, significantly reducing commerce. 

Fort Peck Lake in Montana - Largest Man-Made Lake in Montana 1
Native tribes like the Sioux, Crow, Assiniboine, and Blackfeet once resided on the land Fort Peck Lake now occupies.


In the 1920s, South Dakota, North Dakota, and Montana banded together to advocate for the development of the upper Missouri River by exploring the construction of massive dams on Missouri. 

Construction of the Dam 

President Franklin D. Roosevelt authorized the construction of the Fort Peck Dam. Roosevelt, in 1933, through a presidential order, transferred the federal land to the United States Army Corps of Engineers. This happened after the Great Depression of 1929 when the high unemployment rate became a severe issue. The dam would not only produce jobs, but it would also generate electricity, control floods, and create enormous reservoirs for commercial activity.

The community of Fort Peck transformed into a true boomtown during the construction stage as thousands of people were employed in building the dam. Thousands of individuals from all across the country moved to Montana during the Great Depression in search of work. Over 7,000 men and women stepped forward to work on the dam. In 1936, approximately 11,000 dam workers were employed, and many more flocked to Montana to start enterprises.

In addition, recreation amenities such as campgrounds, smaller ponds, day-use areas, and interpretive sites were developed around the dam. The reservoir and dam were erected between 1933 and 1937, making it the first dam in the upper Missouri River Basin and Montana’s largest man-made Lake.

Animals in Fort Peck Lake

Cisco (Coregonus)
When ciscoes joined Fort Peck Lake in the late 1980s and early 1990s, it increased the number of species in the reservoir.

©Michaela Holubova/Shutterstock.com

According to Montana Fish, Wildlife, and Parks, Fort Peck Reservoir is home to approximately 50 different fish species, some of which are endemic to the Missouri River system, such as sauger and paddlefish. 

Two major bait species — spot tail shiner and cisco — were introduced to Fort Peck Reservoir in the late 1980s and early 1990s. This increased the number of species in the reservoir, which included walleyes, smallmouth bass, northern pike, and several more. 

Charles M. Russell National Wildlife Refuge, where Fort Peck Reservoir is located, is home to a variety of wildlife, including mule deer, elk, bighorn sheep, buffalo, pronghorns, sage grouse, ducks, and bald eagles. Hundreds of elk assemble in the Slippery Ann Wildlife Viewing Area each fall, creating a spectacular sight. 

Recreation at the Fort Peck Lake Park

A large bull North American elk standing in an open meadow
Hunting is common at Fort Peck Lake, and one of the species there for hunters is elk.

©Tony Campbell/Shutterstock.com

Fort Peck Lake offers a variety of outdoor adventures due to its enormous size and seclusion from major urban centers. Hiking, fishing, hunting, camping, and other outdoor activities are available in the Charles M. Russel National Wildlife Refuge. 

  • Hunting: It is common to observe guests hunting around Fort Peck Lake. The wildlife refuge offers good hunting for upland birds, deer, and elk.
  • Fishing: Since there are more than 50 different types of fish, fishing is a very popular hobby. Walleye fishing is particularly popular on Fort Peck Lake. The lake also hosts the annual Governor’s Cup Fishing Competition, which draws fishermen looking for big walleye.
  • Boating: boating is one of the most popular Missouri River and Fort Peck Reservoir activities. But due to the windy conditions, this activity can be hazardous to smaller boats. Boating on Fort Peck Lake needs a powerful and steady boat.
  • Camping: Numerous campgrounds on Fort Peck Lake in Montana offer free camping activities. There are roughly 100 campsites and two primary camping grounds surrounding the Lake. 
  • Hiking: Hiking opportunities abound on the Missouri River paths, including the Beaver Creek Nature Trail and the Hell Creek Trail. Hikers will enjoy the scenery along Fort Peck Lake’s shores. The back roads connect Fort Peck Lake to the rest of the refuge.

Visitors to the Lake can access the area via a paved direct access road directly to the Fort Peck Marina. There’s also a gravel and dirt road that leads to Hell Creek Bay and another road on the southern fork of Rock Creek Bay, just 10 miles west of Highway 24.


Not only is Fort Peck Lake the largest man-made Lake in Montana and the location of the first dam constructed along the Missouri River, but it is also a tourism hotspot. Fort Peck Lake and the National Wildlife Refuge are managed by three agencies: the Bureau of Land Management, the State of Montana, and the Army Corps of Engineers. Several state parks and recreational areas have been built within the refuge, and there are several possibilities for animal viewing and photography throughout the refuge. Hiking, horseback riding, ATV riding, and general exploring are among the popular activities near Fort Peck Lake.

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Fort Peck Lake in Montana, and its surrounding area.
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About the Author

Abdulmumin is a pharmacist and a top-rated content writer who can pretty much write on anything that can be researched on the internet. However, he particularly enjoys writing about animals, nature, and health. He loves animals, especially horses, and would love to have one someday.

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