Linn County Lake Quality
Missouri, 5 lakes, average grade C (Fair)
Linn County holds 5 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Brookfield Lake (A); the most-stressed is Marceline Lake (D).
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Quick Answers for Linn County
Planning a trip? Check special fishing regulations for Brookfield Lake — or check the official Missouri fishing regulations.
All Lakes in Linn County
5 lakes · 3 graded, 2 not rated3 graded lakes · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | ABrookfield LakeLinn | A | 4.4 ft | 19.7 µg/L | 4.9 µg/L | No recent samples | ✓ Public |
| 2 | CJo Shelby LakeLinn | C | No recent samples | 48 µg/L | 15 µg/L | No recent samples | ✓ Public |
| 3 | DMarceline LakeLinn | D | 1.9 ft | 110.9 µg/L | 25.7 µg/L | No recent samples | ✓ Public |
| NRPershing State Park LakeLinn | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBrookfield Country Club LakeLinn | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in Missouri
See how Linn County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.