High Quality Content by WIKIPEDIA articles! Frederick is a city in north-central Maryland. It is the county seat of Frederick County, the largest county by area in the state of Maryland. Frederick is an outlying community of the Washington-Arlington-Alexandria, DC-VA-MD-WV Metropolitan Statistical Area, which is part of a greater Washington-Baltimore-Northern Virginia, DC-MD-VA-WV Combined Statistical Area. The city`s population was 65,239 people at the 2010 census, making it the second largest incorporated area in Maryland behind Baltimore.