The Commonwealth of Pennsylvania , often colloquially referred to as PA by natives and Northeasterners, is a state located in the Northeastern and Middle Atlantic regions of the United States. The state's most populous city is Philadelphia.
Pennsylvania is also nicknamed the "Keystone State" because of the number of important American documents signed in the state (such as the Declaration of Independence). 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).
Another 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. He knew of the hostility Quakers faced when they opposed religious ritual, taking oaths, violence, war and military service, and what they viewed as ostentatious frippery.
Pennsylvania has 51 miles of coastline along Lake Erie and 57 miles of shoreline along the Delaware Estuary.
Climate of Pennsylvania
Pennsylvania's diverse topography also produces a variety of climates. Straddling two major zones, the southeastern corner of the state has the warmest climate. Greater Philadelphia lies at the southernmost tip of the humid continental climate zone, with some characteristics of the humid subtropical climate that lies in Delaware and Maryland to the south. Moving toward the mountainous interior of the state, the climate becomes markedly colder, the number of cloudy days increases, and winter snowfall amounts are greater. Western areas of the state, particularly cities near Lake Erie, can receive over 100 inches of snowfall annually, and the entire state receives plentiful rainfall throughout the year.

