There are 9 US Post Offices in Smith County serving a total of 17,224 residents equating to 1,914 residents per post office. It's estimated that approximately 27,491 packages are handled across the 9 county post offices annually. Smith County is a county located in the U.S. state of Tennessee. As of the 2010 census, the population was 19,166. In the section known as Middle Tennessee, its county seat is Carthage. The county was organized in 1799 and is named for Daniel Smith, a Revolutionary War veteran who made the first map of Tennessee and served as a United States senator. Smith County is part of the Nashville-Davidson\u2013Murfreesboro\u2013Franklin, TN Metropolitan Statistical Area."