St. Louis city County Lake Quality
Wisconsin, 5 lakes, average grade D (Poor)
St. Louis city County has 5 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. On average, St. Louis city County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Boathouse Lake (D) is the cleanest in the county.
Quick Answers for St. Louis city County
Planning a trip? Check special fishing regulations for Boathouse Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
All Lakes in St. Louis city County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Boathouse Lake | D | 2.3 ft | - | 59.8 µg/L |
| 2 | O'Fallon Park Lake | D | 1.6 ft | - | 335 µg/L |
| 3 | Lafayette Park Lake | D | 2.3 ft | - | 127.5 µg/L |
| 4 | Forest Park Pond | D | 1.6 ft | - | 68.8 µg/L |
| 5 | Jefferson Lake | D | - | - | 70 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.