Lakes / Illinois / Cook County / Longjohn Slough
Longjohn Slough, Illinois
53.13 acres
Surface Area
Where It Sits, and How Deep It Goes
Locator - Illinois
41.71 degrees N, 87.88 degrees W - Cook 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 Longjohn Slough Stacks Up
- Larger than 39% of the 511 lakes counted in Illinois.
- About 17 miles from Chicago, as the crow flies.
Lakes Nearby
| Lake | County | Distance | Surface Area |
|---|---|---|---|
| Maple Lake | Cook | 0.6 mi | 57.08 acres |
| Saganashkee Slough | Cook | 1.4 mi | 359.29 acres |
| Tampier Slough | Cook | 4.2 mi | 53.13 acres |
| Tampier Lake | Cook | 4.6 mi | 121.08 acres |
| Orland Lake | Cook | 5.0 mi | 273.39 acres |
| Golfview Lake | DuPage | 6.0 mi | 32.12 acres |
Straight-line distance between lake centers.
Facts and Figures
Questions About Longjohn Slough
How Big Is Longjohn Slough?
Longjohn Slough covers 53.13 acres in Cook County, Illinois.
What Is the Largest Lake in Cook County?
Lake Calumet is the largest lake in Cook County, at 591.91 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 109990704). Verified October 30, 2026.