Pierce County Lake Quality
Minnesota, 1 lakes, average grade B (Good)
Pierce County has 1 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. With an average grade of B, Pierce County sits comfortably above the Minnesota median.
A meaningful share of Pierce's lakes break 50 feet of depth, which matters because deep lakes hold cooler water all summer and resist the resuspended-sediment problems that plague shallow basins. The county's best-graded lake is Lake St Croix (B).
Quick Answers for Pierce County
Planning a trip? Check special fishing regulations for Lake St Croix, whether the fish are safe to eat, and the best times to fish — or browse the full Minnesota regulations index.
All Lakes in Pierce County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Lake St Croix | B | 7.2 ft | 78 ft | 32.5 µg/L |
Other Counties in Minnesota
See how Pierce County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 36 states and 2 Canadian provinces.
Where to stay near Pierce County
Top-rated places to stay near Pierce County
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Source: EPA National Aquatic Resource Surveys, 2026.