Green Hills is a borough in Washington County, Pennsylvania, United States. The borough was formed in 1978 when a local businessman worked to secede from the dry township of South Franklin after voters there defeated a referendum that would allow alcohol sales at his country club. The population was twenty at the time of the 2020 census, makiā¦Green Hills is a borough in Washington County, Pennsylvania, United States. The borough was formed in 1978 when a local businessman worked to secede from the dry township of South Franklin after voters there defeated a referendum that would allow alcohol sales at his country club. The population was twenty at the time of the 2020 census, making it the third least populous borough in the state; only S.N.P.J. and Centralia had fewer residents.