Lakes / Illinois / Effingham County / Altamont Reservoir
Altamont Reservoir, Illinois
42.26 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Illinois
39.04 degrees N, 88.72 degrees W - Effingham 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 Altamont Reservoir Stacks Up
- Larger than 30% of the 511 lakes counted in Illinois.
- About 72 miles from Springfield, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Lake Nellie | Fayette | 6.9 mi | 54.08 acres |
| Lake Sara | Effingham | 8.2 mi | 553.02 acres |
| Lake Pauline | Effingham | 11 mi | 34.1 acres |
| Patterson Lake | Clay | 11 mi | 28.91 acres |
| Forbes Lake | Marion | 22 mi | 523.37 acres |
| Vandalia Municipal Reservoir | Fayette | 23 mi | 627.37 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Altamont Reservoir
How Big Is Altamont Reservoir?
Altamont Reservoir covers 42.26 acres in Effingham County, Illinois.
What Is the Largest Lake in Effingham County?
Lake Sara is the largest lake in Effingham County, at 553.02 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 151830414). Verified October 30, 2026.