Spoon Lake Dam
Spoon Lake Dam is an earth dam located in Knox County, Illinois, built in 1971. It carries a High hazard potential classification.
About Spoon Lake Dam
The primary purpose of Spoon Lake Dam is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Oak Run Property Owners Association (private). It impounds the Trib Spoon River near Williamsfield.
The dam stands 74 feet tall and stretches 1,128 feet across, creates a reservoir covering 610 acres, has a maximum storage capacity of 19,500 acre-feet, and collects water from a drainage area of 17 square miles. Completed in 1971, the structure is well into its service life at over 50 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 74 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 | Williamsfield |
| River/Stream | Trib Spoon River |
| Coordinates | 40.95084, -90.12555 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 74 ft |
| Dam Height | 74 ft |
| Dam Length | 1,128 ft |
| Year Completed | 1971 (55 years old) |
Storage & Hydraulics
| NID Storage | 19,500 acre-ft |
| Max Storage | 19,500 acre-ft |
| Normal Storage | 13,250 acre-ft |
| Surface Area | 610 acres |
| Drainage Area | 17 sq mi |
| Max Discharge | 2,870 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Recreation |
| Owner | OAK RUN PROPERTY OWNERS ASSOCIATION |
| Owner Type | Private |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 09/09/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00422 |
| Federal ID | IL00422 |
| More Info | State Dam Safety Program |