Lakes / Illinois / Mason County / Otter Lake
Otter Lake, Mason County, Illinois
301.22 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Illinois
40.08 degrees N, 90.28 degrees W - Mason County. State and county outlines drawn from Census boundary data; the lake marker is placed by its USGS National Hydrography Dataset coordinates, not by eye. Schematic - not a survey map.
How Otter Lake Stacks Up
- Larger than 83% of the 511 lakes counted in Illinois.
- About 39 miles from Springfield, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Mound Lake | Mason | 1.0 mi | 26.19 acres |
| Wilcox Lake | Mason | 1.5 mi | 51.65 acres |
| Crane Lake | Mason | 2.9 mi | 797.66 acres |
| Swamp Slough | Cass | 3.7 mi | 31.63 acres |
| Eagle Lake | Mason | 3.8 mi | 112.19 acres |
| Ingram Lake | Mason | 3.8 mi | 118.86 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Otter Lake
How Big Is Otter Lake?
Otter Lake covers 301.22 acres in Mason County, Illinois.
What Is the Largest Lake in Mason County?
Quiver Lake is the largest lake in Mason County, at 2,926.49 acres.
Largest Lakes in Illinois
| # | Lake | County | Surface Area | Max Depth |
|---|---|---|---|---|
| 1 | Carlyle Lake | Clinton | 22,796.77 acres | - |
| 2 | Mine Number 21 Reservoir | Franklin | 17,062.04 acres | - |
| 3 | Upper Peoria Lake | Woodford | 15,460.64 acres | - |
| 4 | Lake Shelbyville | Shelby | 10,235.1 acres | - |
| 5 | Crab Orchard Lake | Williamson | 7,292.57 acres | - |
All 511 Illinois lakes ranked by surface area
Sources: USGS National Hydrography Dataset (The National Map) lake data (ID 133214781). Verified October 30, 2026.