There are 11 US Post Offices in Chatham County serving a total of 255,243 residents equating to 23,204 residents per post office. It's estimated that approximately 407,396 packages are handled across the 11 county post offices annually. Chatham County is a county in the U.S. state of Georgia, and is located on the state's Atlantic coast. The county seat and largest city is Savannah. One of the original counties of Georgia, Chatham County was created February 5, 1777, and is named after William Pitt, 1st Earl of Chatham. The U.S. Census Bureau's 2015 population estimate for Chatham County was 286,956 residents, making Chatham the most populous Georgia county outside the Atlanta metropolitan area. In the official 2010 census, the population of Chatham County was 265,128. Chatham is the core county of the Savannah metropolitan area."