Frederick County, Maryland
Frederick County is located in Maryland, United States. As of the 2020 U.S. census, the population was 271,717. The county seat is Frederick. The county is part of the Capital region of the state.
Like other outlying sections of the Washington metropolitan area, Frederick County has experienced a rapid population increase since the 1980s. It borders the southern border of Pennsylvania and the northeastern border of Virginia.
Catoctin Mountain Park in the county is the location of Camp David, a U.S. presidential retreat, and Fort Detrick, a U.S. Army base.