Pennsylvania, officially the Commonwealth of Pennsylvania, is a state located in the northeastern and Mid-Atlantic regions of the United States. The Appalachian Mountains run through Pennsylvania's middle. The Commonwealth is bordered by Delaware to the southeast, Maryland to the south, West Virginia to the southwest, Ohio to the west, Lake Erie and the Canadian province of Ontario to the northwest, New York to the north, and New Jersey to the east. Pennsylvania is the 33rd-largest state by area, and the 6th-most populous state according to the last official US census count in 2010. Pennsylvania's the 9th-most densely populated of the 50 states. There are currently 759 Pennsylvania airports in our database.