There are 29 US Post Offices in Franklin County serving a total of 109,360 residents equating to 3,771 residents per post office. It's estimated that approximately 174,551 packages are handled across the 29 county post offices annually. Franklin County is a county located in South Central Pennsylvania. As of the 2010 census, the population was 149,618. Its county seat is Chambersburg. Franklin County comprises the Chambersburg-Waynesboro, PA Metropolitan Statistical Area, which is also included in the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area. It lies to a large extent within the Cumberland Valley."