The Commonwealth of Pennsylvania , often colloquially referred to as PA (its postal abbreviation which succeeds the archaic Penn. and Penna. as common abbreviations) by natives and Northeasterners, is a state located in the Northeastern and Middle Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Canada to the north, and New Jersey to the east. The state's most populated cities are Philadelphia, Pittsburgh, and Allentown.