Algonquin Dam
Illinois — McHenry County — FOX RIVER
Location
| State | Illinois |
| County | McHenry |
| River | FOX RIVER |
| Coordinates | 42.16574, -88.29009 |
Physical Characteristics
| NID Height | 9 ft |
| Dam Height | 9 ft |
| Dam Length | 300 ft |
| NID Storage | 24,200 acre-ft |
| Max Storage | 24,200 acre-ft |
| Surface Area | — |
Safety Classification
| Hazard Potential | Significant |
| Condition Assessment | Not Available |
| EAP Status | Yes |
| Last Inspection | October 28, 2025 |
| Inspection Frequency | 3 |
Dam Information
| Year Completed | 1947 |
| Primary Purpose | Flood Risk Reduction |
| Dam Type | Concrete |
| Owner Type | State |
| Owner | ILLINOIS DEPARTMENT OF NATURAL RESOURCES |
Location Map
About This Dam Record
Dam safety data is maintained by the Army Corps of Engineers National Inventory of Dams (NID). High-hazard dams are those where failure could cause loss of life or major property damage downstream.