Frederick is a city in north-central Maryland, United States. 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 2010 U.S. Census Bureau count estimated the city's total population at 65,239 people, making it the second largest incorporated area in Maryland behind Baltimore.Frederick is home to Frederick Municipal Airport (FDK), which primarily accommodates general aviation traffic, and to the U.S. Army's Fort Detrick, the largest employer in the county. Frederick is also home to BP Solar, which is the second-largest employer in the county (March 2010, BP Solar laid off hundreds of employees due to setbacks).