The land that would form Chatham County (pronounced: chat 'um) was ceded to the English by the Creeks in the Treaty of Savannah on May 21, 1733, confirmed and expanded by agreements of 1735 and 1736. In 1741, the Trustees of Georgia divided the colony into two counties -- Savannah and Frederica.
The County of Savannah included all of present-day Chatham County southward to the Ogeechee River. This division only lasted a year, as the Trustees in 1742 named William Stephens as president of the entire colony. After the Trustees surrendered their charter in 1752, Georgia became a royal colony.
By an act of March 15, 1758, the colonial legislature created seven parishes. With the outbreak of the American Revolution, Whig forces took control of government in Georgia. On Feb. 5, 1777, they adopted the state's first constitution -- the Constitution of 1777. Article IV of that document transformed the existing colonial parishes into seven counties, with Indian ceded lands forming an eighth county.
Chatham County, which was fifth on the list and thus is considered Georgia's fifth county, consisted of all of Christ Church Parish and that part of Saint Philip Parish south of the Canoochee River.
The county was named in honor of William Pitt, the first Earl of Chatham. Pitt (1708-1778) was British Prime Minister during the French and Indian War. Later, he opposed the Stamp Act and was a popular figure in the American counties.
In 1793, the legislature created Bryan County from the western portion of Chatham County. In 1850, land from Effingham County was annexed to Chatham.