A state of the eastern United States. One of the original Thirteen Colonies, it was explored by Europeans in the early 1600s, settled by Swedes in 1634, and granted by an English royal charter to William Penn in 1681. The Mason-Dixon Line (surveyed in 1763-1767) established the colony's southern boundary and was extended westward in 1784. Pennsylvania played a crucial role in the American Revolution and ratified the US Constitution in 1787. Harrisburg is the capital and Philadelphia the largest city.