The area that today is known as South Fayette Township originally was claimed by both Pennsylvania and Virginia. In 1788, the area became part of Moon Township, one of the seven townships in Allegheny County, Pennsylvania. Two years later, Fayette Township was carved out of Moon Township. The areas that today are known as South Fayette Township and North Fayette Township comprised Fayette Township, named in honor of General Lafayette. In 1842, Fayette Township was split into North Fayette and South Fayette townships. South Fayette was officially established March 16, 1842, and celebrated its 175th anniversary in 2017. Following the creation of Collier Township in 1875, South Fayette Township's territorial limits as they stand today are formed by the Washington County line, Robinson Run, Coal Run and Chartiers Creek.