There are 4 US Post Offices in Decatur County serving a total of 10,677 residents equating to 2,669 residents per post office. It's estimated that approximately 17,042 packages are handled across the 4 county post offices annually. Decatur County is a county located in the U.S. state of Tennessee. As of the 2010 census, the population was 11,757. Its county seat is Decaturville.