Cleanest Lakes in Minnesota & Wisconsin
Top 50 cleanest lakes — 25 from each state — ranked by 2026 water quality data. Grades combine Secchi clarity (water transparency), total phosphorus (nutrient load), and chlorophyll-a (algae density) into a single 0–100 score. Higher score, cleaner water.
State-specific lists: Minnesota → Wisconsin → Related: Best swimming lakes → Clearest by Secchi depth →
| Rank | Lake | County | State | Grade | Clarity | Phosphorus | Area |
|---|---|---|---|---|---|---|---|
| 1 | East Fox Lake | Crow Wing | MN | A | 16.1 ft | 10 µg/L | 240.88 acres |
| 2 | Deep Portage Lake | Cass | MN | A | 15.4 ft | 10 µg/L | 129.02 acres |
| 3 | Little Wabana Lake | Itasca | MN | A | 23.8 ft | 6.5 µg/L | 115.73 acres |
| 4 | Clearwater Lake | Cook | MN | A | 30 ft | 4 µg/L | 461.73 acres |
| 5 | Lower Hay Lake | Crow Wing | MN | A | 19 ft | 13 µg/L | 700.21 acres |
| 6 | Latoka Lake | Douglas | MN | A | 19 ft | 11 µg/L | 766.63 acres |
| 7 | Bad Medicine Lake | Becker | MN | A | 25 ft | 6 µg/L | 803.03 acres |
| 8 | Big Sugar Bush Lake | Becker | MN | A | 17 ft | 10 µg/L | 521.51 acres |
| 9 | Pelican Lake | Otter Tail | MN | A | 16.1 ft | 15 µg/L | 4.0K acres |
| 10 | Fullers Lake: East Basin | Beltrami | MN | A | 15 ft | 9.5 µg/L | - |
| 11 | Birch Lake | Wright | MN | A | 15 ft | 17 µg/L | 99.82 acres |
| 12 | Birch Lake | Cook | MN | A | 18 ft | 8 µg/L | 236.31 acres |
| 13 | Round Lake | Cook | MN | A | 16.5 ft | 8.5 µg/L | 154.48 acres |
| 14 | Round Lake | Beltrami | MN | A | 18 ft | 7 µg/L | 181.06 acres |
| 15 | Pike Lake | Cook | MN | A | 17.8 ft | 6 µg/L | 814.43 acres |
| 16 | Whitefish Lake | Crow Wing | MN | A | 15.1 ft | 14 µg/L | 7.7K acres |
| 17 | Long Lake | Clearwater | MN | A | 20 ft | 7 µg/L | 158.86 acres |
| 18 | Long Lake | Cass | MN | A | 21.5 ft | 9 µg/L | 1.0K acres |
| 19 | Long Lake | Beltrami | MN | A | 20 ft | 7 µg/L | 411.95 acres |
| 20 | Long Lake | Becker | MN | A | 20 ft | 8 µg/L | 414.51 acres |
| 21 | Long Lake | Itasca | MN | A | 16.7 ft | 8 µg/L | 155.28 acres |
| 22 | Long Lake | Itasca | MN | A | 16.9 ft | 10 µg/L | 134.49 acres |
| 23 | Dead Lake | Hubbard | MN | A | 16 ft | 10 µg/L | 130.64 acres |
| 24 | Unnamed Lake | Otter Tail | MN | A | 15.1 ft | 9 µg/L | 1.4K acres |
| 25 | Maple Lake | Itasca | MN | A | 15.3 ft | 10 µg/L | 254.55 acres |
| 26 | Geneva Lake | Walworth | WI | A | 20.2 ft | 13 µg/L | 5.4K acres |
| 27 | Round Lake | Sawyer | WI | A | 21.1 ft | 14.4 µg/L | 3.3K acres |
| 28 | Round Lake | Oconto | WI | A | 16.8 ft | 13.8 µg/L | 31 acres |
| 29 | Deep Lake | Adams | WI | A | 15.5 ft | 13.3 µg/L | 33 acres |
| 30 | Beasley Lake | Waupaca | WI | A | 18.4 ft | 15.1 µg/L | 12 acres |
| 31 | Bass Lake | Washburn | WI | A | 16 ft | 12.3 µg/L | 132 acres |
| 32 | Bass Lake | Oconto | WI | A | 16.8 ft | 10.7 µg/L | 145 acres |
| 33 | Clear Lake | Sawyer | WI | A | 17 ft | 11.2 µg/L | 77 acres |
| 34 | Clear Lake | Polk | WI | A | 15.5 ft | 13.9 µg/L | 30 acres |
| 35 | Clear Lake | Lincoln | WI | A | 18 ft | 10.6 µg/L | 259 acres |
| 36 | Explosion Lake | Oconto | WI | A | 17 ft | 15.7 µg/L | 43 acres |
| 37 | Sugar Camp Lake | Oneida | WI | A | 16.5 ft | 10.3 µg/L | - |
| 38 | Little Spider Lake | Vilas | WI | A | 16 ft | 11.5 µg/L | 223 acres |
| 39 | Rosalind Lake | Vilas | WI | A | 19.3 ft | 9.9 µg/L | - |
| 40 | Lake Lucerne | Forest | WI | A | 18.5 ft | 9.3 µg/L | 1.0K acres |
| 41 | Two Island Lake | Chippewa | WI | A | 15.3 ft | 15.1 µg/L | 29 acres |
| 42 | Long Lake | Bayfield | WI | A | 16.2 ft | 13.7 µg/L | 280 acres |
| 43 | Long Lake | Burnett | WI | A | 21.5 ft | 11.3 µg/L | 222 acres |
| 44 | Lake Metonga | Forest | WI | A | 22 ft | 14 µg/L | 2.0K acres |
| 45 | Anderson Lake | Vilas | WI | A | 21 ft | 10.4 µg/L | 35 acres |
| 46 | Archibald Lake | Oconto | WI | A | 17.6 ft | 10.6 µg/L | 392 acres |
| 47 | Carlin Lake | Vilas | WI | A | 21 ft | 7.3 µg/L | 155 acres |
| 48 | Wolf Lake | Adams | WI | A | 15 ft | 13.1 µg/L | 42 acres |
| 49 | Butternut Lake | Forest | WI | A | 19.5 ft | 11.8 µg/L | 1.2K acres |
| 50 | Green Lake | Oconto | WI | A | 18.3 ft | 17.9 µg/L | 21 acres |
Frequently Asked Questions
What are the cleanest lakes in the US?
There is no single national ranking — water quality is graded state-by-state by different agencies using different metrics. LakeQuality grades Minnesota and Wisconsin lakes using a uniform A–F scale based on Secchi depth (clarity), total phosphorus, and chlorophyll-a — the three signals scientists use to measure lake health. The lakes ranked here have the highest combined scores in our 2026 dataset.
How do you rank the cleanest lakes?
We score every monitored lake on three water-quality signals: Secchi depth (water clarity, deeper is better), total phosphorus (lower is better — phosphorus drives algae growth), and chlorophyll-a (lower is better — measures algae density). Each signal gets a 0–100 sub-score; the three are averaged into an overall score that maps to an A–F grade. Lakes here are ranked by their overall score.
Is a clean lake safe to swim in?
Generally yes — lakes with grade A or B and chlorophyll-a below 10 µg/L are unlikely to host harmful algal blooms during normal conditions. But water quality changes seasonally. Always check for posted advisories before swimming, especially in late summer when blue-green algae blooms peak.
What is Secchi depth?
Secchi depth is a clarity measurement. A black-and-white disk is lowered into the water; the depth at which it disappears (in feet or meters) is the Secchi depth. Greater depth means clearer water. In Minnesota and Wisconsin, A-grade lakes typically have Secchi depths above 10 feet.
Why is Minnesota called the Land of 10,000 Lakes?
Minnesota actually has about 11,842 lakes ≥10 acres — far more than the marketing slogan suggests. Wisconsin has roughly 15,000 named lakes by some counts (including very small ones). Combined, the two states cover more freshwater lakes than nearly any equivalent area in North America.