Frederick County, Maryland Frederick County, Maryland Frederick County is located in the northern part of the U.S. state of Maryland. As of the 2010 U.S. Census, the population was 240,336. The county seat is Frederick. Frederick County is included in the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area. Like other outlying sections of the Washington metropolitan area, Frederick County has experienced a rapid population increase in recent years. It borders the southern border of Pennsylvania and the northeastern border of Virginia. The county is home to Catoctin Mountain Park (encompassing the presidential retreat Camp David) and to the U.S. Army's Fort Detrick. It has also
Harmony Hall (Fort Washington, Maryland) stage plays, art exhibits, arts classes, scout meetings, and other cultural programs. The building was originally an elementary school. Harmony Hall (Fort Washington, Maryland) Harmony Hall, located in Fort Washington, Maryland, is managed by the United States National Park Service as part of the National Capital Parks-East system. It has been a National Park Service site since 1966. Harmony Hall is a -story Georgian country house built of red brick during the eighteenth century. It is surrounded by of land on Broad Creek, a Potomac River tributary. The house was built circa 1769 by Enoch Magruder. After his death, the