Pennsylvania, officially the Commonwealth of Pennsylvania, is a state located in the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. The state borders Delaware to its southeast, Maryland to its south, forming the Mason–Dixon line, West Virginia to its southwest, Ohio to its west, the Canadian province of Ontario to its northwest via Lake Erie, New York to its north, and the Delaware River and New Jersey to its east. Pennsylvania is the fifth-most populous U.S. state, home to over 13 million residents as of the 2020 United States census, and the ninth-highest state by population density. It is the 33rd-largest state by land area. The largest metropolitan statistical area is the Philadelphia metropolitan area/Delaware Valley, centered on Philadelphia, the state's most populous city and sixth-most populous U.S. city, and an expanding biopharmaceutical, commercial, educational, entrepreneurial/venture capital, industrial, and transportational hub. Pennsylvania's second-largest metropolitan area, Greater Pittsburgh, is centered in and around Pittsburgh, also a biopharmaceutical hub and the Commonwealth's second-largest city. Geographically situated between the two larger metros lies Harrisburg, the capital city of Pennsylvania.
Pennsylvania's geography is highly diverse. The Appalachian Mountains run through the center of the state, the Allegheny and Pocono mountains span much of Northeastern Pennsylvania, and approximately 59% of the state is forested. Although Pennsylvania technically has no oceanic shoreline, it has 140 miles (225 km) of waterfront along Lake Erie and along the tidal Delaware River, the latter of which reaches the Delaware Bay, a marginal bay of the Atlantic Ocean.
Pennsylvania was founded in 1681 through a royal land grant to William Penn, the son of the commonwealth's namesake. Before that, between 1638 and 1655, a southeast portion of the state was part of New Sweden, a Swedish colony. Established as a haven for religious and political tolerance, the British colonial-era Province of Pennsylvania was known for its relatively peaceful relations with native tribes, innovative government system, and religious pluralism. Pennsylvania played a vital historical role in the American Revolution and the ultimately successful quest for independence from the British Empire, hosting the First and Second Continental Congress in Philadelphia, the latter of which formed the Continental Army commanded by George Washington in 1775, during the American Revolutionary War, unanimously adopted the Declaration of Independence the following year. On December 12, 1787, Pennsylvania was the second state to ratify the U.S. Constitution after Delaware.
In the 21st century, Pennsylvania has garnered the nickname "Cellicon State" for the central role of Philadelphia and Pittsburgh in the development of technology and immunotherapies to treat different cancers. AI and STEM education are recognized to hold high-priority status for Pennsylvania's long-term mission and future.
Pennsylvania's history of human habitation extends thousands of years before the foundation of the colonial Province of Pennsylvania in 1681. Archaeologists believe the first settlement of the Americas occurred at least 15,000 years ago, during the Last Glacial Period, though it is unclear when humans first inhabited present-day Pennsylvania. Between 10,000 and 16,000 years ago, Native Americans crossed the two continents, arriving in North America. Meadowcroft Rockshelter in Jefferson Township includes the earliest known signs of human activity in Pennsylvania and perhaps all of North America, including the remains of a civilization that existed over 10,000 years ago and possibly pre-dated the Clovis culture. By 1000 AD, in contrast to their nomadic hunter-gatherer ancestors, the native population of Pennsylvania had developed agricultural techniques and a mixed food economy.
By the time European colonization of the Americas began, at least two major Native American tribes inhabited Pennsylvania. The first, the Lenape, spoke an Algonquian language and inhabited the eastern region of the state, then known as Lenapehoking. It included most of present-day New Jersey and the Lehigh Valley and Delaware Valley regions in eastern and southeastern Pennsylvania. The Lenape's territory ended somewhere between the Delaware River in the east and the Susquehanna River in central Pennsylvania. The second tribe, the Susquehannock, spoke an Iroquoian language and were based in Eastern Pennsylvania along the Susquehanna River. European disease and constant warfare with several neighboring tribes and groups of Europeans weakened these two tribes, and they were grossly outpaced financially as the Wendat and Haudenosaunee blocked them from proceeding west into Ohio during the Beaver Wars. As they lost numbers and land, the Wendat abandoned much of their western territory and moved closer to the Susquehanna River, and the Haudenosaunee and Mohawk tribes moved further north. The Iroquoian Petun was northwest of the Allegheny River.
In the 17th century, the Dutch and the English claimed both sides of the Delaware River as part of their colonial lands in America. The Dutch were the first to take possession. By June 3, 1631, the Dutch began settling the Delmarva Peninsula by establishing the Zwaanendael Colony on the site of present-day Lewes, Delaware. In 1638, Sweden established the New Sweden Colony in the region of Fort Christina on the site of present-day Wilmington, Delaware. New Sweden claimed and, for the most part, controlled the lower Delaware River region, including parts of present-day Delaware, New Jersey, and Pennsylvania, but settled few colonists there.
On March 12, 1664, King Charles II of England gave James, Duke of York a grant that incorporated all lands included in the original Virginia Company of Plymouth Grant and other lands. This grant was in conflict with the Dutch claim for New Netherland, which included parts of today's Pennsylvania.
On June 24, 1664, the Duke of York sold the portion of his large grant that included present-day New Jersey to John Berkeley and George Carteret for a proprietary colony. The land was not yet in British possession, but the sale boxed in the portion of New Netherland on the West side of the Delaware River. The British conquest of New Netherland began on August 29, 1664, when New Amsterdam was coerced to surrender while facing cannons on British ships in New York Harbor. The conquest was completed in October 1664, when the British captured Fort Casimir in what today is New Castle, Delaware. The Treaty of Breda between England, France, and the Netherlands confirmed the English conquest on July 21, 1667, although there were temporary reversions.
On September 12, 1672, during the Third Anglo-Dutch War, the Dutch reconquered New York Colony/New Amsterdam, establishing three County Courts, which went on to become original Counties in present-day Delaware and Pennsylvania. The one that later transferred to Pennsylvania was Upland. This was partially reversed on February 9, 1674, when the Treaty of Westminster ended the Third Anglo-Dutch War and reverted all political situations to the status quo ante bellum. The British retained the Dutch Counties with their Dutch names. By June 11, 1674, New York reasserted control over the outlying colonies, including Upland, and the names started to be changed to British names by November 11, 1674. Upland was partitioned on November 12, 1674, producing the general outline of the current border between Pennsylvania and Delaware.
On February 28, 1681, Charles II granted a land charter to Quaker leader William Penn to repay a debt of £16,000 (around £2,100,000 in 2008, adjusting for retail inflation) owed to William's father. The transaction represents one of the largest land grants to an individual in history. Penn proposed that the land be called New Wales, but there were objections to that name, so he recommended Sylvania (from the Latin silva: "forest, woods"). The King named it Pennsylvania (literally "Penn's Woods") in honor of Admiral Penn. The younger Penn was embarrassed at this name, fearing that people would think he had named it after himself, but King Charles would not rename the grant. Penn established a government with two innovations, the county commission and freedom of religion, which were subsequently replicated in many of the Thirteen Colonies.