LaSalle Lake, a manmade, 2,058-acre lake 8 miles southeast of Marseilles, is popular among anglers. Serving as a cooling lake for Commonwealth Edison's LaSalle Power Station, the lake is formed by levees that rise above the surrounding land. While this "perched" construction helps the lake catch the wind to cool the impounded water, it can result in extremely hazardous conditions for unwary boaters. All lake users should familiarize themselves with the precautions described in the "Safety Information" below.

Dirt excavated for the lake's construction was used to build the shoreline and internal dikes, which are covered with rock riprap. The dikes are used to direct cooling water through a five day circulation pattern from the discharge channel back to the intake channel. There is typically a 20-degree water temperature difference between the two channels. The average depth of LaSalle Lake is 15 feet, but there are excavated areas within the lake up to 70 feet deep.

With its riprapped shoreline, LaSalle has no natural shoreline for beaching boats. Boaters must allow ample time to boat from the lake's northern shores to the boat ramp area on the southwestern corner.