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 (see Delaware).

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.

After 1718 the Scotch-Irish began colonizing in the Cumberland Valley and gradually pushed the frontiers toward W Pennsylvania. Their rugged independence and the peculiarities of their frontier problems made them rebellious against the established order. Throughout the province agriculture was the chief occupation, although industry was spurred by abundant water power and plentiful natural resources.

In the west settlement was hindered by a growing unrest among the Native Americans. Penn's heirs lacked both the good sense and the ethical values that prompted Penn's fair and considerate treatment. Resentful of encroachment on their lands and of the land purchase made by the Albany Congress (1754), the Native Americans allied themselves with the French, who were then fortifying positions in the Ohio valley (see French and Indian Wars). The frontier settlements were severely ravaged until, after several reverses, the French abandoned (1758) Fort Duquesne to British and American forces under Gen. John Forbes.

The power of the Native Americans was not completely broken until the suppression of the uprising of 1763 (see Pontiac's Rebellion). The inept defenses provided by the Quaker-controlled assembly during the crisis aroused bitter resentment and intensified efforts to overturn proprietary rule. The struggle between proprietary and antiproprietary parties was soon overshadowed, however, by the opposition to British imperial policies that culminated in the American Revolution.

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 (see Brandywine, battle of) 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.

Opposition to federal taxation in rural Pennsylvania led to violence in the Whiskey Rebellion of 1794 and the Fries Rebellion of 1798 (see Fries, John), while anti-eastern sentiment forced removal of the state capital to Lancaster in 1799, then to Harrisburg in 1812. Western influence in state affairs increased as the rapid movement of settlers into the Ohio country created new markets, stimulated the growth of new industries, and assured the importance of Pittsburgh and Erie as commercial centers. The economic and social development of W Pennsylvania also encouraged programs of internal improvements. The turnpike era, initiated by the incorporation of the Lancaster Turnpike in 1792, was followed by an extensive canal-building program in the 1820s and 30s and, after the introduction of steam power, by an era of extensive railroad construction.

Adequate provisions for free public education, championed by Gov. George Wolf and Thaddeus Stevens, emerged in the Free School Act of 1834, which was implemented in 1849 by legislation making attendance by those of school age compulsory. Much of the early education was denominational, and many schools remained church-affiliated.

In political life the Democratic party was generally dominant, and in 1857 Pennsylvania gave the nation a Democratic president in James Buchanan. However, a split within the party over its opposition to slavery and the desire for a high protective tariff to protect the state's growing industries led to a Republican victory in 1860 and began Pennsylvania's long affiliation with the Republican party. Because of Pennsylvania's location near the South, it was the scene of several battles in the Civil War, notably the Gettysburg campaign of 1863.

With the close of the war came the rapid emergence of the state as a mighty industrial commonwealth. Supported by high protective tariffs, the industries found favorable markets and a constant supply of immigrant labor. The first oil well was dug at Titusville in 1859, and a number of fortunes, particularly that of the Rockefeller family, was founded on petroleum. But it was steel that became the basic industry, using iron ore from the Lehigh valley and the Bethlehem area and the native Pennsylvania coal. Later the iron ore was transported in massive amounts across the Great Lakes. Under the manipulation of such men as Andrew Carnegie, Henry Frick, Charles Schwab, and J. Pierpont Morgan (1837–1913; see under Morgan, family) numerous interests were merged into vast combines with state and national influence.

In the face of this increasing concentration of power, labor struggled to achieve safer working conditions, higher wages, and shorter hours. The campaign brought bloodshed during the fight between mine owners and the radical Molly Maguires and reached a climax in the strike at Homestead (see Homestead strike) in 1892. The miners, under the leadership of John Mitchell and aided by the intervention of Theodore Roosevelt, achieved a qualified victory in the anthracite strike of 1902, but the great steel strike of 1919 was broken. During the 1930s the Congress of Industrial Organizations (CIO) successfully promoted unionization in many new areas and somewhat weakened the strength of the American Federation of Labor (AFL). By 1941 the CIO had succeeded in organizing the steel industry, while the United Mine Workers had acquired increasing strength among the workers in the coal fields.

The powerful and corrupt political machine that had been built by Simon Cameron continued into the 20th cent. under the leadership of such bosses as Boies Penrose. Gifford Pinchot, a Progressive Republican and a vigorous dry, was governor for two terms (1923–27, 1931–35) and did much to repair government through a new administrative code, an improved budget system, and pioneer work in conservation.

In 1979 the state suffered a near-disaster as an accident at the Three Mile Island nuclear facility near Harrisburg resulted in a partial meltdown. Pennsylvania's population has grown slowly since the 1940s, when it was the second largest state in the union; it was the sixth most populous state after the 2000 census. After losing hundreds of thousands of manufacturing jobs in the 1980s, the state's economy experienced a notable shift to the service sector. Some of Pennsylvania's enterprises did grow, however, and in recent years such high-tech industries as biotechnology and pharmaceuticals have flourished, largely in the suburbs of Philadelphia and Pittsburgh.

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