Important Pennsylvanians of both dominant political parties emerged as leaders of the Revolutionary movement—Benjamin Franklin, Benjamin Rush, Joseph Reed, Thomas Mifflin, John Dickinson, Robert Morris, and Haym Salomon. In 1776 a provincial convention dominated by radical patriots created the Commonwealth of Pennsylvania under one of the most democratic of the new state constitutions.
The state was invaded by British troops, and notable engagements were fought in 1777 on the Brandywine and at Germantown. Philadelphia was occupied by the British, while Valley Forge witnessed the heroic endurance of Washington’s troops in the winter of 1777–78, making the site a shrine of patriotism. In the postwar period, Pennsylvania’s role as the geographical keystone of the new nation was strengthened by its resolution of boundary disputes that had persisted throughout the colonial period: agreement was reached with Maryland in 1784 by acceptance of the Mason-Dixon line; with Virginia and New York in 1786; with the United States and the Iroquois Confederacy in 1789; and with Connecticut in 1799 after bitter dissension in the Wyoming Valley.
Philadelphia, host to the First and Second Continental Congresses (1774, 1775–81) and scene of the signing of the Declaration of Independence, was for many years the nation’s leading city. It was the site of the Constitutional Convention of 1787, served as the seat of the new federal government from 1790 to 1800, and became a financial center through the organization of the First Bank of the United States (1791) and the U.S. Mint (1792). In 1790 it was also the site of a convention that replaced the radical state constitution of 1776 with a more conservative one patterned after the federal Constitution, while retaining such liberal achievements as the act (1780) providing for the gradual abolition of slavery. Philadelphia was not, however, typical of the state as a whole.
A devout Quaker who had suffered for his beliefs, Penn viewed his colony as a holy experiment, designed to grant asylum to the persecuted under conditions of equality and freedom. In 1681 he sent William Markham as his deputy to establish a government at Uppland and sent instructed commissioners to plot the City of Brotherly Love (Philadelphia), which was laid out a few miles north of the confluence of the Delaware and the Schuylkill rivers.
Penn carefully constructed a constitution, known as the Frame of Government, that gave Pennsylvania the most liberal government in the colonies. Religious freedom was guaranteed to all who believed in God, a humane penal code was adopted, and the emancipation of slaves was encouraged. However, under the representative system that it established, the popular assembly was left in an inferior position in relation to the executive branches controlled by the proprietors. In 1682 Penn arrived at Uppland (renamed Chester). Shortly thereafter he met with the chiefs of the Delaware tribes and a famous treaty was signed that promoted long-lasting goodwill between the Native Americans and the European settlers. After Penn’s death in 1718 proprietary rights were held by his heirs.
By this time Pennsylvania had developed into a dynamic and growing colony, enriched by the continuous immigration of numerous different peoples. The Quakers, English, and Welsh were concentrated in Philadelphia and the eastern counties, where they acquired great commercial and financial power through foreign trade and where they achieved a political dominance which they held until the time of the American Revolution. Philadelphia had by then become the finest city in the nation, a leader in the arts and the professions. The Germans (Pennsylvania Dutch)—largely of the persecuted religious sects of Mennonites (including Amish), Moravians, Lutherans, and Reformed—settled in the farming areas of SE Pennsylvania, where they retained their cohesion and to a considerable extent their language, customs, architecture, and superstitions.
In the early 1600s the English, Dutch, and Swedes disputed the right to the region of Pennsylvania. Explorations were confined to the Delaware River vicinity, where fur trading with the Native Americans was carried on. The original permanent settlement was established on Tinicum Island (1643) in the Delaware River by Johan Printz, governor of New Sweden, and was followed in the succeeding years by the neighboring colony of Uppland.
Swedish jurisdiction was short-lived as the Dutch, operating from their stronghold in New Amsterdam, succeeded in gaining control of the Middle Atlantic region in 1655. In turn the Dutch were overpowered by the British forces of Col. Richard Nicolls, acting for the duke of York (later James II), and in 1664 the British took over the Delaware area. The duke of York remained in control until 1681, when, in payment of a royal debt, William Penn was granted proprietary rights to almost the whole of what is now Pennsylvania, and, in addition, leased the three Lower Counties.