Lake Bernard Frank (Lake Frank), is a 54-acre (220,000 m²) reservoir on the North Branch of Rock Creek in Derwood, Maryland, United States, just east of Rockville. It is named after Bernard Frank, a wilderness activist and a co-founder of The Wilderness Society. The lake's boundaries are, approximately, Route 28, East Gude Drive, Avery Road, and Muncaster Mill Road. Lake Frank was created in 1966 to aid in flood and sediment control, as well as to provide recreation. It has an earthen dam, installed in 1967, on its southern side. It was created as a sister lake to Lake Needwood.