Chatham County encompasses the site of Oglethorpe's first landing in what was to become the Colony of Georgia. After the break with England, Chatham was the third county to be designated, comprising lands from Christ Church and St. Phillip parishes in 1777. It is named for one of England's most illustrious prime ministers, William Pitt, Earl of Chatham. Savannah, the county seat, is derived from a Spanish word meaning grassy plain.