Argyle Lake Dam
Argyle Lake Dam is an earth dam located in McDonough County, Illinois, built in 1949. It carries a Significant hazard potential classification.
About Argyle Lake Dam
The primary purpose of Argyle Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Illinois Department Of Natural Resources (state). It impounds the East Fork La Moine River near Colchester.
The dam stands 58 feet tall and stretches 670 feet across, creates a reservoir covering 114 acres, has a maximum storage capacity of 4,040 acre-feet, and collects water from a drainage area of 623 square miles. Completed in 1949, the structure is well-established, with more than 75 years of service.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. An emergency action plan is in place for this dam. The most recent inspection on record was 05/09/2025.
At 58 feet, this dam is taller than 95% of all dams in the United States.
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Location
| State | Illinois |
| County | McDonough |
| Nearest City | Colchester |
| River/Stream | East Fork La Moine River |
| Coordinates | 40.44932, -90.78813 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 58 ft |
| Dam Height | 58 ft |
| Dam Length | 670 ft |
| Year Completed | 1949 (77 years old) |
Storage & Hydraulics
| NID Storage | 4,040 acre-ft |
| Max Storage | 4,040 acre-ft |
| Normal Storage | 2,200 acre-ft |
| Surface Area | 114 acres |
| Drainage Area | 623 sq mi |
| Max Discharge | 13,580 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | ILLINOIS DEPARTMENT OF NATURAL RESOURCES |
| Owner Type | State |
| Hazard Classification | Significant |
| Condition Assessment | Not Available |
| Last Inspection | 05/09/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00270 |
| Federal ID | IL00270 |
| More Info | State Dam Safety Program |