There are 25 US Post Offices in Frederick County serving a total of 165,404 residents equating to 6,616 residents per post office. It's estimated that approximately 264,003 packages are handled across the 25 county post offices annually. Frederick County is a county 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. The county is sometimes associated with Western Maryland, depending on the definition used. 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 been the home to several celebrated historical figures like Francis Scott Key, Chris Rose, Zach Taylor, Matt Bennett, Thomas Johnson, Roger B. Taney, and Barbara Fritchie."