Lake Mcmaster Dam
Lake Mcmaster Dam is an earth dam located in Knox County, Illinois, built in 1981. It carries a High hazard potential classification.
About Lake Mcmaster Dam
The primary purpose of Lake Mcmaster 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 Snakeden Creek near Dahinda.
The dam stands 81 feet tall and stretches 850 feet across, creates a reservoir covering 178 acres, has a maximum storage capacity of 5,350 acre-feet, and collects water from a drainage area of 2 square miles. Completed in 1981, the structure is 45 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. An emergency action plan is in place for this dam. The most recent inspection on record was 09/09/2025.
At 81 feet, this dam is taller than 97% of all dams in the United States.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Illinois dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Illinois |
| County | Knox |
| Nearest City | Dahinda |
| River/Stream | Snakeden Creek |
| Coordinates | 41.00508, -90.07193 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 81 ft |
| Dam Height | 81 ft |
| Dam Length | 850 ft |
| Year Completed | 1981 (45 years old) |
Storage & Hydraulics
| NID Storage | 5,350 acre-ft |
| Max Storage | 5,350 acre-ft |
| Normal Storage | 4,920 acre-ft |
| Surface Area | 178 acres |
| Drainage Area | 2 sq mi |
| Max Discharge | 4,125 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | ILLINOIS DEPARTMENT OF NATURAL RESOURCES |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 09/09/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL50344 |
| Federal ID | IL50344 |
| More Info | State Dam Safety Program |