Frederick County, Maryland, founded in 1748, is located in the north central part of Maryland and is 664 square miles in area (the largest of Maryland’s counties). Frederick County has a population of 243,675, according to the U.S. Census 2014 estimate. The county seat, and largest of the 12 incorporated municipalities, is the City of Frederick which is located 45 miles northwest of Washington, D.C. and 45 miles west of Baltimore.