Taking up less than a square mile, historic Harmony Borough was established in 1804 and incorporated in 1840. Its historic district is on the National Register of Historic Places.
The seven member council meets on the first Tuesday of every month. The borough also has the Historic Architectural Review Board, which is responsible for reviewing any changes to building in the borough's Historic District. Police coverage is provided to borough residents by the Zelienople Police Department.
Harmony was founded by the German pietist Johann Georg Rapp and his Harmony Society in 1804. Most of the borough's rich history, particulary that of the Harmony Society, is preserved at The Harmony Musuem.