The Historical Markers Program was authorized by the
Commonwealth of Pennsylvania when it created Pennsylvania Historical Commission (PHC), the precursor of the
Pennsylvania Historical and Museum Commission (PHMC), through the Act of the General Assembly No. 777, on July 25, 1913. The PHC was empowered to mark by proper monuments, tablets, or markers, places or buildings within the Commonwealth where historical events transpired. The earliest markers were bronze plaques often mounted on large stones gathered from the Pennsylvania countryside. Philadelphia architect
Paul Philippe Cret designed later bronze plaques that included the state's
coat of arms with text laid out within a rectangular double border. Starting in 1945, markers were cast of
aluminum, used gold-colored text of raised characters on a deep blue background within a silver-colored frame, and were initially affixed to concrete posts, so as to be more easily seen by motorists alongside roads. Eventually smaller and narrower city markers were added for their better suitability in urban settings. ==Listings of markers by county==