[2] The lake is located in east-central South Dakota, on the Coteau des Prairies and is within the watershed of the Vermillion River.

[3] By the early 1990s, it had grown to cover (at times) 20,000 acres (81 km2), becoming the largest natural lake in the state.

[4] The lake is the location of a state recreation area managed by the South Dakota Department of Game, Fish, and Parks which includes camping facilities.

[3] A popular destination for anglers, game fish in the lake include walleye, northern pike, yellow perch and sunfish.

[2] The area is an important habitat for fish and waterfowl, and Lake Thompson has been named a National Natural Landmark.