L & N Reservoir
L & N Reservoir is an earth dam located in Jefferson County, Illinois, built in 1910. It carries a High hazard potential classification.
About L & N Reservoir
The primary purpose of L & N Reservoir is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by City Of Mount Vernon (local government). It impounds the Trib Casey Fork near Mount Vernon.
The dam stands 25 feet tall and stretches 720 feet across, and has a maximum storage capacity of 353 acre-feet. Completed in 1910, the structure is over a century 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 05/27/2025.
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 | Jefferson |
| Nearest City | Mount Vernon |
| River/Stream | Trib Casey Fork |
| Coordinates | 38.32171, -88.91495 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 25 ft |
| Dam Height | 25 ft |
| Dam Length | 720 ft |
| Year Completed | 1910 (116 years old) |
Storage & Hydraulics
| NID Storage | 353 acre-ft |
| Max Storage | 353 acre-ft |
| Normal Storage | 182 acre-ft |
| Max Discharge | 607 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | CITY OF MOUNT VERNON |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Not Available |
| Last Inspection | 05/27/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IL00173 |
| Federal ID | IL00173 |
| More Info | State Dam Safety Program |