Jack Lake

Jack Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI value of 37 puts Jack Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's 110 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. The lake's 142 acres and 2.5 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Jack Lake ranks 42 of 133 in Cass County — solidly in the upper half of the local distribution.

Jack 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 Jack Lake, one of 13 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.