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
Comptroller of the Treasury of Maryland v. Wynne collected by the state's comptroller of the treasury. Residents who earn income outside of Maryland may receive a credit against the state, but not the county income tax for income taxes paid on that income to other states. Nonresidents who earn income in Maryland must pay the state income tax and, in lieu of the county income tax, a "special nonresident tax" that was set at a rate "equal to the lowest county income tax rate set by any Maryland county." In 2006, Maryland residents Brian and Karen Wynne, a married couple, earned income from other states through an S