The state park consists of two sites: one encompasses 250-acre (100 ha) St. Mary's Lake; the second covers 2,200 acres (890 ha) and is largely undeveloped.

The park is managed by the Maryland Department of Natural Resources.

[2] The state acquired land for the park's first site between 1968 and 1974, with the lake being constructed in 1975.

[3] The park features fishing, non-motorized boating, canoeing, picnicking, and hunting.

A 7.5-mile (12.1 km) trail around St. Mary's Lake is used for hiking, horseback riding, and mountain biking.