Lakes / Illinois / Macoupin County / Old Mount Olive Reservoir
Old Mount Olive Reservoir, Illinois
35.34 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Illinois
39.09 degrees N, 89.74 degrees W - Macoupin 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 Old Mount Olive Reservoir Stacks Up
- Larger than 20% of the 511 lakes counted in Illinois.
- About 48 miles from Springfield, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Mount Olive Lake | Macoupin | 1.4 mi | 39.54 acres |
| Staunton Reservoir | Macoupin | 3.3 mi | 83.77 acres |
| Walton Lake | Montgomery | 6.6 mi | 29.16 acres |
| Old Gillespie Lake | Macoupin | 7.4 mi | 68.7 acres |
| New Gillespie Lake | Macoupin | 8.5 mi | 205.34 acres |
| Smith Reservoir | Macoupin | 11 mi | 63.75 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Old Mount Olive Reservoir
How Big Is Old Mount Olive Reservoir?
Old Mount Olive Reservoir covers 35.34 acres in Macoupin County, Illinois.
What Is the Largest Lake in Macoupin County?
Otter Lake is the largest lake in Macoupin County, at 419.34 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 79317786). Verified October 30, 2026.