There are 5 US Post Offices in Grainger County serving a total of 23,667 residents equating to 4,733 residents per post office. It's estimated that approximately 37,775 packages are handled across the 5 county post offices annually. Grainger County is a county located in the U.S. state of Tennessee. As of the 2010 census, the population was 22,657. Its county seat is Rutledge. It is renowned for its tomatoes. Grainger County is included in the Knoxville, TN Metropolitan Statistical Area."