There are 25 US Post Offices in Franklin County serving a total of 83,756 residents equating to 3,350 residents per post office. It's estimated that approximately 133,684 packages are handled across the 25 county post offices annually. Franklin County is a nongovernmental county located in the U.S. state of Massachusetts. As of the 2010 census, the population was 71,372, which makes it the least-populous county on the Massachusetts mainland, and the third-least populous county in the state. Its largest community and traditional county seat is Greenfield. Franklin County comprises the Greenfield Town, MA Micropolitan Statistical Area, which is included in the Springfield-Greenfield Town, MA Combined Statistical Area."