Loon Lake

Loon Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Cook County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

Trophically, Loon Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. At 202 ft of maximum depth, Loon Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. With 1,095 acres of surface and 14.3 miles of shoreline, Loon Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Among the 128 graded lakes in Cook County, Loon Lake ranks 13 — in the top quartile locally.

Loon Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Walleye are documented at Loon Lake, one of 10 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.