There are 6 US Post Offices in Franklin County serving a total of 17,172 residents equating to 2,862 residents per post office. It's estimated that approximately 27,408 packages are handled across the 6 county post offices annually. Franklin County is a county located along the eastern border of the U.S. state of Indiana. It was formed in 1811 and consists of 13 townships. Its county seat is Brookville. As of 2010, the population was 23,087. The county seat is Brookville. Franklin County is part of the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area.