This subcategory is devoted to Pennsylvania, the Keystone State, so-called due to its strategic position on the Eastern seaboard and its prominent role in the economic, political, and military history of the United States.

Pennsylvania's 117,412 sq km of terrain is dominated by mountain chains in the west and a broad coastal plain in the east. The largest city is Philadelphia, a major port; southeast PA is the fifth largest metropolitan area in the US. Pittsburgh, in the west, is a major steel producing city. The capital is Harrisburg.

Pennsylvania's famed steel mills take advantage of its leading role in the production of coal and lime. Manufacturing dominates the economy, followed by agriculture.

The second of original 13 states to ratify the Constitution, in 1787, Pennsylvania had originally been settled by the Lenape (Delaware), Shawnee, and Susquehanna peoples. The Swedish established a colony in 1643, conquered by the Dutch in 1655 and by the English in 1664, who ceded the land to the Quaker William Penn to found a colony.

Pennsylvania became a major battleground during the French and Indian Wars. Prominent scientist, humanist, and diplomat Benjamin Franklin was among those who helped make Philadelphia a center of revolutionary activity in the late 18th century. The Declaration of Independence and Constitution were both written in Philadelphia.

Pennsylvania was also the site of the Battle of Gettysburg, considered the turning point in the American Civil War, and the burgeoning steel industry-- and the labor movement that accompanied the development of manufacturing.