Little Armstrong Lake

Little Armstrong Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in St. Louis County. 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.

Trophically, Little Armstrong Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. Little Armstrong Lake reaches 26 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 70 acres, Little Armstrong Lake sits below the Minnesota median: a small water where shoreline activity has an outsized effect on water quality. Little Armstrong Lake ranks 9 of 187 in St. Louis County, putting it in the upper tier of locally monitored lakes.

No invasive species are currently listed at Little Armstrong Lake — the lake remains off the Minnesota infested-waters roster. The fishery is bass-led, with 2 documented species across the lake's records. The lake lacks a documented public access point, so visitor use is limited. 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.