Data Report · Updated July 2026
The State of America’s Lakes 2026
Across 9,387 monitored lakes in 13 US states, 44.9% earn a water-quality grade of A or B, while 32% score D or F. The single cleanest lake in the 2026 dataset is East Fox Lake (MN); the worst algae hotspot is Lake Wooldridge (MO).
National grade distribution
Cleanest lakes in America
Highest combined water-quality score, 2026.
- 1.AEast Fox Lake — Crow Wing County, MN16.4 ft clarity · 10 µg/L P
- 2.ANorth Long Lake — Crow Wing County, MN15.1 ft clarity · 14 µg/L P
- 3.ABad Medicine Lake — Becker County, MN25.0 ft clarity · 6 µg/L P
- 4.ABig Sugar Bush Lake — Becker County, MN16.5 ft clarity · 10 µg/L P
- 5.ARound Lake — Cook County, MN16.5 ft clarity · 9 µg/L P
- 6.ARound Lake — Beltrami County, MN18.0 ft clarity · 7 µg/L P
- 7.AHorseshoe Lake — Cass County, MN21.0 ft clarity
- 8.ALong Lake — Cass County, MN21.5 ft clarity · 9 µg/L P
- 9.ALong Lake — Clearwater County, MN20.5 ft clarity · 7 µg/L P
- 10.ALong Lake — Beltrami County, MN20.0 ft clarity · 7 µg/L P
Most-polluted lakes
Lowest combined water-quality score among monitored lakes.
- 1.FKabetogama Lake — St. Louis County, MN2.6 ft clarity
- 2.FNorth Long Lake — Ramsey County, MN2.5 ft clarity · 102 µg/L P
- 3.FSnelling Lake — Hennepin County, MN1.8 ft clarity · 99 µg/L P · 54 µg/L chl-a
- 4.FHorseshoe Lake — Rice County, MN2.0 ft clarity
- 5.FLong Lake — Stearns County, MN2.5 ft clarity · 325 µg/L P
- 6.FLong Lake — Cottonwood County, MN1.0 ft clarity
- 7.FLong Lake — Hennepin County, MN3.3 ft clarity · 90 µg/L P
- 8.FLong Lake — Dakota County, MN1.6 ft clarity · 110 µg/L P · 82 µg/L chl-a
- 9.FJonathan Lake — Carver County, MN1.5 ft clarity · 158 µg/L P
- 10.FPeltier Lake — Anoka County, MN2.5 ft clarity · 374 µg/L P
Worst algae hotspots
Highest measured chlorophyll-a (algae) concentration.
- 1.FLake Wooldridge — Saline County, MO778 µg/L chlorophyll-a
- 2.FPomme de Terre Lake — Hickory County, MO361 µg/L chlorophyll-a
- 3.FBee Tree Lake — St. Louis County, MO296 µg/L chlorophyll-a
- 4.FBuffalo Lake — Pierce County, ND220 µg/L chlorophyll-a
- 5.FKnox Village Lake — Jackson County, MO194 µg/L chlorophyll-a
- 6.FMckay Park Lake — Cole County, MO187 µg/L chlorophyll-a
- 7.FArdmore Lake — Hennepin County, MN185 µg/L chlorophyll-a
- 8.FCrowder S.P. Lake — Grundy County, MO176 µg/L chlorophyll-a
- 9.FLimpp Lake — Gentry County, MO167 µg/L chlorophyll-a
- 10.FLoose Park Lake — Jackson County, MO160 µg/L chlorophyll-a
Clearest water
Deepest measured Secchi (clarity) reading.
- 1.AAdams Lake — Vilas County, WI100.0 ft clarity
- 2.ASt James Pit Lake — St. Louis County, MN47.6 ft clarity
- 3.AClear Lake — Rock County, WI37.5 ft clarity
- 4.ABear Lake Southeast Basin — Kalkaska County, MI36.5 ft clarity
- 5.AHiggins Lake East Basin — Roscommon County, MI35.0 ft clarity
- 6.AHiggins Lake Northwest Basin — Roscommon County, MI34.5 ft clarity
- 7.AWhitefish Bay Deep Lake — Chippewa County, MI34.4 ft clarity
- 8.AHiggins Lake — Roscommon County, MI34.0 ft clarity
- 9.ABear Lake — Kalkaska County, MI33.0 ft clarity
- 10.ACrystal Lake — Benzie County, MI32.0 ft clarity
Biggest improvers
Lakes trending toward better water quality over time.
- 1.ABig Sugar Bush Lake — Becker County, MN16.5 ft clarity · 10 µg/L P
- 2.ARound Lake — Cook County, MN16.5 ft clarity · 9 µg/L P
- 3.ARound Lake — Beltrami County, MN18.0 ft clarity · 7 µg/L P
- 4.AHorseshoe Lake — Cass County, MN21.0 ft clarity
- 5.ALong Lake — Becker County, MN19.3 ft clarity · 8 µg/L P
- 6.AWest Twin Lake — Crow Wing County, MN20.0 ft clarity
- 7.AStar Lake — Crow Wing County, MN19.0 ft clarity · 11 µg/L P
- 8.AStar Lake — Otter Tail County, MN17.0 ft clarity · 13 µg/L P
- 9.AFish Lake — Otter Tail County, MN18.0 ft clarity · 12 µg/L P
- 10.ABirch Lake — Wright County, MN15.0 ft clarity · 17 µg/L P
Biggest decliners
Lakes trending toward worse water quality over time.
- 1.FLong Lake — Stearns County, MN2.5 ft clarity · 325 µg/L P
- 2.FClear Lake — Meeker County, MN3.0 ft clarity · 140 µg/L P
- 3.FClear Lake — Waseca County, MN2.5 ft clarity · 151 µg/L P
- 4.FEagle Lake — Carver County, MN2.0 ft clarity · 169 µg/L P
- 5.FFish Lake — Kanabec County, MN2.0 ft clarity
- 6.FHook Lake — McLeod County, MN2.5 ft clarity
- 7.FGrace Lake — Carver County, MN2.6 ft clarity · 92 µg/L P
- 8.FRhine Lake — Pine County, MN2.5 ft clarity
- 9.FMud Lake — Hennepin County, MN3.0 ft clarity · 196 µg/L P
- 10.FSand Lake — Stearns County, MN2.5 ft clarity
State-by-state summary
Ranked by the share of lakes earning an A or B grade. Open any state for its full report.
| State | Lakes | Avg grade | % A/B | % impaired | Cleanest lake |
|---|---|---|---|---|---|
| Michigan | 628 | B | 67.2% | 44.1% | Windover Lake South Basin; Freeman Township |
| Wisconsin | 1,422 | C | 58% | 36.4% | Geneva Lake |
| New York | 189 | C | 53.4% | 52.4% | Main Section Lake |
| Minnesota | 2,403 | C | 50.8% | 69.5% | East Fox Lake |
| Florida | 2,195 | C | 32.4% | 0% | Highlands-Sirena Lake |
| North Dakota | 150 | C | 28% | 27.3% | Spiritwood Lake |
| Missouri | 317 | C | 25.2% | 42.6% | Lake Capri |
| South Dakota | 4 | D | 25% | 0% | Traverse Lake |
| Indiana | 22 | D | 22.7% | 68.2% | Grand Calumet Lagoon Lake |
| Illinois | 144 | D | 16.7% | 77.8% | Axehead Lake |
| Iowa | 170 | D | 7.1% | 68.8% | West Okoboji Lake |
| Ohio | 17 | D | 0% | 29.4% | Caesar Creek Lake |
| Pennsylvania | 3 | D | 0% | 100% | — |
How the grades are calculated
Each lake is graded A–F on three measured indicators — Secchi clarity, total phosphorus, and chlorophyll-a — drawn from the EPA Water Quality Portal and state environmental agencies. Northern-tier states use Metropolitan Council thresholds; Florida uses Florida LAKEWATCH breakpoints for naturally productive subtropical lakes. Full method: methodology.
Cite this report: LakeQuality, “The State of America’s Lakes 2026,” lakequality.org/report. Data: EPA Water Quality Portal + state agencies.
Coverage note: this report grades monitored lakes in 13 states, not every lake in the United States. Grades reflect the most recent multi-year sampling available and update as new agency data is ingested.