The Commonwealth of Pennsylvania is one of five Middle Atlantic States in the United States of America.

One of Pennsylvania's nicknames is the Quaker State; in colonial times, it was known officially as the Quaker Province, in recognition of Quaker William Penn's First Frame of Government constitution for Pennsylvania that guaranteed liberty of conscience. Penn knew of the hostility Quakers faced when they opposed rituals, oaths, violence, and ostentatious frippery.

Pennsylvania has also been known as the Keystone State since 1802, based in part upon its central location among the original Thirteen Colonies forming the United States. It was also a keystone state economically, having both the industry common to the North, making such wares as Conestoga wagons and rifles, and the agriculture common to the South, producing feed, fiber, food, and tobacco.

Pennsylvania has 51 miles (82 km) of coastline along Lake Erie and 57 miles (92 km) of shoreline along the Delaware Estuary. Philadelphia is Pennsylvania's largest city and is home to a major seaport and shipyards on the Delaware River.