Frederick is the county seat of Frederick County, the largest county by area in the State of Maryland. Frederick has been an important crossroads community since it was located in colonial times at the intersection of an important north-south Indian trail, and east-west routes to the Chesapeake Bay both at Baltimore and what became Washington, D.C. and across the Appalachian mountains to the Ohio River watershed. The gateway to western Maryland is now within 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 United States Census, making it the second-largest incorporated city in Maryland, behind only Baltimore.
Frederick is home to Frederick Municipal Airport (IATA: FDK), which primarily accommodates general aviation traffic, and to the county's largest employer U.S. Army's Fort Detrick bioscience and communications research installation.