Pennsylvania is a state located in the Northeastern, Great Lakes, Appalachian, and Mid-Atlantic regions of the United States. The Appalachian Mountains run through its 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 5th-most populous state according to the most recent official U.S. Census count in 2010. It is the 9th-most densely populated of the 50 states. Pennsylvania's two most populous cities are Philadelphia (1,580,863), and Pittsburgh (302,407). The state capital and its 10th-largest city is Harrisburg. Pennsylvania has 140 miles (225 km) of waterfront along Lake Erie and the Delaware River.