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
Maryland of the American Revolutionary War (1775–1783), on February 2, 1781, Maryland became the last and 13th state to approve the ratification of the Articles of Confederation and Perpetual Union, first proposed in 1776 and adopted by the Second Continental Congress in 1778, which brought into being the United States as a united, sovereign and national state. It also became the seventh state admitted to the Union after ratifying the new federal Constitution in 1788. In December 1790, Maryland donated land selected by first President George Washington to the federal government for the creation of the new national capital of Washington,