Pennsylvania , which, but for a small stretch on Lake Erie is the only landlocked state in the northeast, was explored by the Dutch in the early 1600s, settled by the Swedes forty years later, and claimed by the British in 1664. Charles II of England, who owed a debt to the Penn family, rid himself of the potentially troublesome young William Penn , an enthusiastic advocate of religious freedom, by granting him land in the colony in 1682. Penn Jr. immediately established a "holy experiment" of "brotherly" love and tolerance, naming the state for his father and setting a good example by signing a peaceful cohabitation treaty with the Native Americans. Most of the early agricultural settlers were religious refugees: Quakers like Penn himself, Mennonites from Germany and Switzerland, to be joined later by Irish Catholics during the potato famines of the nineteenth century.. "The keystone state" was crucial in the development of the US. Politicians and thinkers like Benjamin Franklin congregated in Philadelphia - home of both the Declaration of Independence and the Constitution - and were prominent in articulating the ideas behind the Revolution. Later, the battle in Gettysburg, south Pennsylvania - best remembered for Abraham Lincoln's immortal Gettysburg Address - marked a turning point in the Civil War. Pennsylvania was also vital industrially: Pittsburgh, in the west, was the world's leading steel producer in the nineteenth century, and nearly all the nation's anthracite coal is still mined here. The two great urban centers of Philadelphia and Pittsburgh , both lively and vibrant tourist destinations, are at opposite ends of the state. The three hundred miles between them, though predominantly agricultural, are topographically diverse. There are over one hundred state parks, with green rolling countryside in the east, brooding forests in the west, and in the northeast, the rivers, lakes and valleys of the Poconos. Lancaster County , home to traditional Amish farmers, and the Gettysburg battlefield both heave with busloads of day-trippers, while the Hershey chocolate factory, minutes away from Harrisburg , the capital, draws thousands of cocoa-loving visitors each year.