Spirit Lake

Spirit Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. Spirit Lake reaches 20 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 73 acres, Spirit Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Within Vilas County's 202 graded waters, Spirit Lake sits at rank 23, near the top of the local distribution.

Spirit Lake has no invasive species recorded in Wisconsin state databases as of 2024, though prevention practices still apply at all access points. The lake's fish records list 1 species — a varied community without one dominant gamefish. 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.