Montana Lake Named One of the Cleanest in USA. Yes, It’s Gorgeous
Hopefully, you had the chance to spend a weekend or two this summer at one of Montana's awesome lakes. We have over 3,000 named lakes in Big Sky Country (including reservoirs, if you want to get technical), from the massive Fort Peck Reservoir to smaller, underrated gems.
Some Montana lakes, you may have hiked for miles, arriving to find yourself the lone person with a fly rod, high in the hills, surrounded by the most beautiful scenery in the country.
Other, easily accessible lakes might be packed on weekends with a mix of wake boats, jet skis, campers, pontoon boats, fishermen, and families, all enjoying the water.
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What do you think is the cleanest lake in Montana?
I feel like most of the lakes in Montana are relatively clear. But how clean are they? Popular Canyon Ferry gets pretty green by mid-summer, as do several other hotspots.
And many Montana lakes receive plenty of agricultural runoff. The water might look fairly clear, but if it's full of pesticides or cow manure, it's not really "clean", is it?
Lake Koocanusa named 6th Cleanest Lake in the United States
Travel+Leisure just shared the cleanest lakes in America report from Lake.com, and the 2026 ranking puts Lake Koocanusa in the top 10. This fun-to-say, 28,722-acre lake scored points based on eight factors: dissolved oxygen, ammonia, lead, phosphorus, sulfate, total dissolved solids, turbidity, and pH.
The word Koocanusa means something, right?
Yeah, but probably not in the way you might think. Lake Koocanusa didn't exist until 1972, when the dam was completed. Developed by a partnership between the USA and Canada, the stunning lake spans the border in Northwest Montana/Southern British Columbia.
But the lake's name is completely made up.
They held a contest to name the new reservoir, and a resident from Libby, Montana, won. The clever individual took these words: Kootenay River, Canada, and USA, and essentially mashed them together.
You might be pronouncing it wrong.
Supposedly, the correct way to pronounce Lake Kucanoosa is: Coo-can-you-S-A. Not coo-kah-noose-ah. Now I feel dumb for saying it wrong my entire life.
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Gallery Credit: Dave Steel