Chatham County is the easternmost county in the U.S. state of Georgia, 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 official 2020 population for Chatham County was 295,291 residents. This was an increase of 11.4% from the official 2010 population of 265,128 residents.