Philadelphia ( FIL-ə-DEL-fee-ə), colloquially referred to as Philly, is the most populous city in the U.S. state of Pennsylvania and the sixth-most populous city in the United States. Its population was 1.60 million at the 2020 census and estimated at 1.57 million in 2025. The Philadelphia metropolitan area, also known as the Delaware Valley, is located in both the Mid-Atlantic and northeastern United States; home to 6.33 million residents, it is the nation's ninth-largest metropolitan area. Philadelphia is known for its culture, cuisine, and history, maintaining contemporary influence in technology and business, sports, and music.
Philadelphia was founded in 1682 by William Penn, an English Quaker and advocate of religious freedom, and served as the capital of the colonial era Province of Pennsylvania. It then played a vital role during the American Revolution and Revolutionary War. It served as the central meeting place for the nation's Founding Fathers in hosting the First Continental Congress (1774) and the Second Continental Congress, during which the Founders formed the Continental Army, elected George Washington as its commander, and adopted the Declaration of Independence on July 4, 1776. During the Revolutionary War's Philadelphia campaign, the city fell to the British Army, which occupied Philadelphia for nine months from September 1777 to June 1778. Following the end of the Revolutionary War, the U.S. Constitution was ratified at the Philadelphia Convention. Philadelphia remained the largest U.S. city until 1790, and it served as the nation's first capital from May 10, 1775, until December 12, 1776, and on four subsequent occasions until 1800, when construction of the new national capital in Washington, D.C. was completed.
With 17 four-year universities and colleges in the city, Philadelphia is one of the nation's leading centers for higher education and academic research. As of 2023, the Philadelphia metropolitan area had a gross metropolitan product of US$557.6 billion and is home to 13 Fortune 500 corporate headquarters. Metropolitan Philadelphia ranks as one of the nation's Big Five tech venture capital hubs, facilitated by its proximity central to both the financial ecosystems of New York City and the regulatory environment of Washington, D.C. Metropolitan Philadelphia is also a biotechnology hub and has garnered the nickname "Cellicon Valley" for its central role in the development of immunotherapies to treat different cancers. The Philadelphia Stock Exchange, owned by Nasdaq since 2008, is the nation's oldest stock exchange and a global leader in options trading. 30th Street Station, an important national railway crossroads, is the third-busiest Amtrak rail hub in the U.S., handling over 5.5 million passengers in 2025. In part aided by its central Mid-Atlantic U.S. geolocation, Philadelphia International Airport has become the largest transatlantic hub for American Airlines. The city's multimodal transportation and logistics infrastructure also includes the expanding PhilaPort seaport, and Interstate 95, the spine of the north–south highway axis linking the cities of the U.S. Eastern Seaboard.
Philadelphia has a culturally and philanthropically active LGBTQ+ community. The city has also played an influential historic and ongoing role in the development and evolution of American music, especially R&B, soul, and rock. The city hosts more outdoor sculptures and murals than any other city in the nation. Fairmount Park, when combined with adjacent Wissahickon Valley Park in the same watershed, has an area of 2,052 acres (830 ha), representing one of the nation's largest urban parks and the world's 55th largest. With five professional sports teams and one of the nation's most loyal and passionate fan bases, Philadelphia is often ranked as the nation's best city for professional sports fans.
Philadelphia is a city of many firsts, including the nation's first library (1731), hospital (1751), medical school (1765), national capital (1774), university (by some accounts) (1779), central bank (1781), stock exchange (1790), zoo (1874), and business school (1881). Philadelphia hosts 67 National Historic Landmarks, including Independence Hall. From the city's 17th century founding through the present, Philadelphia has been the birthplace of or home to many prominent and influential Americans.
History
Native peoples
Before the arrival of Europeans in the early 17th century, the Lenape, an Indian tribe also known as the Delaware Indians, lived in the village of Shackamaxon in present-day Philadelphia and the surrounding area. The Lenape historically lived along the Delaware River watershed, western Long Island, and the Lower Hudson Valley. Most Lenape were pushed out of the region during the 18th century as the original Thirteen Colonies expanded, which was further exacerbated by losses from intertribal conflicts. Lenape communities were also weakened by newly introduced diseases, mainly smallpox, and conflicts with Europeans. The Iroquois occasionally fought the Lenape. Surviving Lenape moved west into the upper Ohio River basin. Following the American Revolutionary War and the subsequent establishment of the United States, the Lenape began moving further west. In the 1860s, the U.S. federal government sent most remaining Lenape in the eastern United States to the Indian Territory in present-day Oklahoma and surrounding territories as part of the Indian removal policy.
Colonial era
Europeans first entered Philadelphia and the surrounding Delaware Valley in the early 17th century. The first settlements were founded by Dutch colonists, who built Fort Nassau on the Delaware River in 1623 in what is now Brooklawn, New Jersey. The Dutch considered the entire Delaware River valley to be part of their New Netherland colony. In 1638, Swedish settlers led by renegade Dutch established the colony of New Sweden at Fort Christina, located in present-day Wilmington, Delaware, and quickly spread out in the valley. In 1644, New Sweden supported the Susquehannocks in their war against Maryland colonists. In 1648, the Dutch built Fort Beversreede on the west bank of the Delaware, south of the Schuylkill River near the present-day Eastwick section of Philadelphia, to reassert their dominion over the area. The Swedes responded by building Fort Nya Korsholm, or New Korsholm, named after a town in Finland with a Swedish majority.
In 1655, a Dutch military campaign led by New Netherland Director-General Peter Stuyvesant took control of the Swedish colony, ending its claim to independence. The Swedish and Finnish settlers continued to have their own militia, religion, and court, and to enjoy substantial autonomy under the Dutch. An English fleet captured the New Netherland colony in 1664, though the situation did not change substantially until 1682, when the area was included in William Penn's charter for Pennsylvania.
In 1681, in partial repayment of a debt, Charles II of England granted Penn a charter for what would become the Pennsylvania colony. Despite the royal charter, Penn bought the land from the local Lenape in an effort to establish good terms with the Native Americans and ensure peace for the colony. Penn made a treaty of friendship with Lenape chief Tammany under an elm tree at Shackamaxon, in what is now the city's Fishtown neighborhood. Penn named the city Philadelphia, which is Greek for 'brotherly love', derived from the Ancient Greek terms φίλος phílos ('beloved, dear') and ἀδελφός adelphós ('brother, brotherly'). There were a number of cities named Philadelphia (Φιλαδέλφεια) in the Eastern Mediterranean during the Greek and Roman periods, including modern Alaşehir, mentioned as the site of an early Christian congregation in the Book of Revelation. As a Quaker, Penn had experienced religious persecution and wanted his colony to be a place where anyone could worship freely. This tolerance, which exceeded that of other colonies, led to better relations with the local native tribes and fostered Philadelphia's rapid growth into America's most important city.
Penn planned a city on the Delaware River to serve as a port and place for government. Hoping that Philadelphia would become more like an English rural town instead of a city, Penn laid out roads on a grid plan to keep houses and businesses spread far apart with areas for gardens and orchards.
The city's inhabitants did not follow Penn's plans, however, and instead crowded the present-day Port of Philadelphia on the Delaware River and subdivided and resold their lots. Before Penn left Philadelphia for the final time, he issued the Charter of 1701 establishing it as a city. Though poor at first, Philadelphia became an important trading center with tolerable living conditions by the 1750s. Benjamin Franklin, a leading citizen, helped improve city services and founded new ones that were among the first in the nation, including a fire company, library, and hospital.
A number of philosophical societies were formed, which were centers of the city's intellectual life, including the Philadelphia Society for Promoting Agriculture (1785), the Pennsylvania Society for the Encouragement of Manufactures and the Useful Arts (1787), the Academy of Natural Sciences (1812), and the Franklin Institute (1824). These societies developed and financed new industries that attracted skilled and knowledgeable immigrants from Europe.
American Revolution
Philadelphia's importance and central location in the colonies made it a natural center for America's revolutionaries. By the 1750s, Philadelphia surpassed Boston as the largest city and busiest port in British America, and the second-largest city in the entire British Empire after London. In 1774, as resentment of the British government's policies towards the colonies and support for independence began burgeoning in the colonies, Philadelphia hosted the First Continental Congress at Carpenters' Hall, and 12 of the original 13 colonies sent delegates to the Congress.
From 1775 to 1781, Philadelphia hosted the Second Continental Congress, whose 56 delegates unanimously adopted the Declaration of Independence inside what was then called Pennsylvania State House and was later renamed Independence Hall. Written predominantly by Thomas Jefferson from his second-floor apartment on Market Street within walking distance of Independence Hall, the Declaration has been described by Pulitzer Prize-winning historian Joseph Ellis as "the most potent and consequential words in American history," and its adoption represented a declaration of war against Great Britain. Since the Declaration's July 4, 1776, adoption, its signing has been cited globally and repeatedly by various peoples of the world seeking independence and liberty. It also has been, since its adoption, the basis for annual celebration by Americans; in 1938, this celebration of the Declaration was formalized as Independence Day, one of only eleven designated U.S. federal holidays.
After George Washington's defeat at the Battle of Brandywine in Chadds Ford Township, on September 11, 1777, during the Philadelphia campaign, the revolutionary capital of Philadelphia was defenseless, and the city prepared for what was perceived to be an inevitable British attack. Because bells could easily be recast into munitions, the Liberty Bell, then known as the Pennsylvania State Bell, and bells from two Philadelphia churches, Christ Church and St. Peter's Church, were hastily taken down and transported by heavily guarded wagon train out of the city. The Liberty Bell was taken to Zion German Reformed Church in Northampton Town, which is present-day Allentown, where it was hidden under the church's floor boards for nine months from September 1777 until departure of British forces from Philadelphia in June 1778. Two Revolutionary War battles, the Siege of Fort Mifflin, fought between September 26 and November 16, 1777, and the Battle of Germantown, fought on October 4, 1777, took place within Philadelphia's city limits.
In Philadelphia, the Second Continental Congress adopted the Articles of Confederation on November 15, 1777. Independence Hall in Philadelphia was the meeting place for the Constitutional Convention, which ratified the Constitution on September 17, 1787, which is now the longest-standing codified national constitution.
Philadelphia served as capital of the United States on five separate occasions between 1776 and 1800—in sum, most of the colonial and early post-colonial period, including the decade before 1800, when Washington, D.C., became the national capital. In 1793, the largest yellow fever epidemic in U.S. history killed about 4,000 to 5,000 people in Philadelphia, or about ten percent of the city's population at the time.
The state capital was moved from Philadelphia to Lancaster in 1799, then ultimately to Harrisburg in 1812. Philadelphia remained the nation's largest city until the late 18th century. It also was the nation's financial and cultural center until ultimately being eclipsed in total population by New York City in 1790. In 1816, the city's free Black community founded the African Methodist Episcopal Church, the first independent Black denomination in the country, and the first Black Episcopal Church. The free Black community also established many schools for its children with the help of Quakers. Large-scale construction projects for new roads, canals, and railroads made Philadelphia the first major industrial city in the United States.
19th century
Throughout the 19th century, Philadelphia hosted a variety of industries and businesses; one of the largest was the textile industry. Major corporations in the 19th and early 20th centuries included the Baldwin Locomotive Works, William Cramp & Sons Shipbuilding Company, and the Pennsylvania Railroad. Established in 1870, the Philadelphia Conveyancers' Association was chartered by the state in 1871. Along with the U.S. Centennial in 1876, the city's industry was celebrated in the Centennial Exposition, the first official World's fair in the U.S.
Immigrants, mostly from Ireland and Germany, settled in Philadelphia and the surrounding districts. These immigrants were largely responsible for the first general strike in North America in 1835, in which workers in the city won the ten-hour workday. The city was a destination for thousands of Irish immigrants fleeing the Great Famine in the 1840s; housing for them was developed south of South Street and later occupied by succeeding immigrants. They established a network of Catholic churches and schools and dominated the Catholic clergy for decades. Anti-Irish, anti-Catholic nativist riots erupted in Philadelphia in 1844. The rise in population of the surrounding districts helped lead to the Act of Consolidation of 1854, which extended the city limits from the 2 square miles (5.2 km2) of Center City to the roughly 134 square miles (350 km2) of Philadelphia County.
In the latter half of the 19th century and leading into the 20th century, immigrants from Russia, Eastern Europe, and Italy, and African Americans from the southern U.S. settled in the city.
Philadelphia was represented by the Washington Grays in the American Civil War. The African-American population of Philadelphia increased from 31,699 to 219,559 between 1880 and 1930, largely stemming from the Great Migration from the South.
20th century
By the 20th century, Philadelphia had an entrenched Republican political machine and a complacent population. In 1910, a general strike shut down the entire city.
In 1917, following outrage over the election-year murder of a Philadelphia police officer, the City Council shrank from two houses to just one. In July 1919, Philadelphia was one of more than 36 industrial cities nationally to suffer a race riot during Red Summer in post-World War I unrest as recent immigrants competed with Black residents for jobs. In the 1920s, the public flouting of Prohibition laws, organized crime, mob violence, and corrupt police involvement in illegal activities led to the appointment of Brig. Gen. Smedley Butler of the U.S. Marine Corps as the city's director of public safety, but political pressure still prevented long-term success in fighting crime and corruption.