St. Mary's River State Park is a public recreation area located in St. Mary's County, Maryland. The state park consists of two sites: one encompasses 250-acre (100 ha) St. Mary's Lake (an automated gate wants $3 for Marylanders, $5 for others); the second covers 2,200 acres (890 ha) and is largely undeveloped. The park is managed by the Maryland Department of Natural Resources.