Montana is full of beautiful bodies of water, but which lake is the deepest?

Mission Mountains
Photo by Colter Olmstead on Unsplash

When you think of large lakes in Montana, some of the first that come to mind are Flathead Lake, Lake McDonald, Canyon Ferry, and Fort Peck. However, none of the lakes listed above take the cake for deepest in Montana.

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Flathead Lake is the largest natural freshwater lake in the western U.S., and one of the 300 largest lakes in the world. It's almost 28 miles long and 15 miles wide in some areas. According to, the lake reaches depths up to 370 feet.

Lake McDonald is the largest lake in Glacier National Park. It's 10 miles long and reaches a maximum depth of 472 feet.


Canyon Ferry Lake has an average depth of 58 feet, and a maximum depth of 160 feet near the dam, according to Montana FWP.

Fort Peck in the eastern part of the state is roughly 134 miles long and has a maximum depth of 220 feet when full. Another interesting fact about Fort Peck is that there are over 1,520 miles of shoreline, which is longer than the California coast.

So, if none of the lakes listed above is the deepest in Montana, which lake is it? It's located in northwest Montana near Whitefish, and most people probably haven't heard of it. There are hundreds of alpine lakes in the area, but the deepest is Tally Lake, which reaches a maximum depth of 492 feet.

Jesse James
Jesse James

To put it in perspective, the tallest building in Montana, the First Interstate Center in Billings, is 272 feet tall. That's pretty wild for a natural alpine lake.

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