There are 6 US Post Offices in Washington County serving a total of 20,783 residents equating to 3,464 residents per post office. It's estimated that approximately 33,172 packages are handled across the 6 county post offices annually. Washington County is a county located in the U.S. state of Georgia. As of the 2010 census, the population was 21,187. The county seat is Sandersville. The county was established on February 25, 1784. It was named for Revolutionary War general (and later President of the United States) George Washington."