Frederick County is a county located in the northern part of the U.S. state of Maryland, bordering the southern border of Pennsylvania and the northeastern border of Virginia. As of the 2010 U.S. Census, the population was 233,385. It is a part of the Washington Metropolitan Area, yet is also sometimes recognized as part of Western Maryland. The county is home to Catoctin Mountain Park (encompassing the presidential retreat Camp David) and to the U.S. Army's Fort Detrick. The county seat is Frederick, which was home to several celebrated historical figures like Francis Scott Key, Thomas Johnson, Roger B. Taney, and Barbara Fritchie. The county (and the county seat) may have been named for Frederick Calvert, 6th Baron Baltimore.