Pennsylvania is a state located in the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, Maryland to its south, West Virginia to its southwest, Ohio to its west, Ontario via Lake Erie to its northwest, New York to its north, and New Jersey to its east. The state capital is Harrisburg, while Philadelphia serves as its most populous city. Pennsylvania's geography is highly diverse, featuring the Appalachian Mountains running through the center, with the Allegheny and Pocono mountains spanning much of the Northeastern region.

The state was founded in 1681 through a royal land grant to William Penn, who established it as a haven for religious and political tolerance. Before this, between 1638 and 1655, a southeast portion was part of the Swedish colony New Sweden. Pennsylvania played a vital role in the American Revolution, hosting the First and Second Continental Congresses in Philadelphia. On December 12, 1787, it became the second state to ratify the U.S. Constitution after Delaware, cementing its early political significance in the nation's formation.

Notable landmarks include Valley Forge, Gettysburg National Military Park, and Independence Hall in Philadelphia, which houses the Liberty Bell. The Battle of Gettysburg in July 1863 was the bloodiest battle of the American Civil War, resulting in over 51,000 casualties. The state also features the Delaware Water Gap National Recreation Area and the Johnstown Flood National Memorial. Major cities like Pittsburgh, known as the Steel City, and Philadelphia define the urban landscape, while the interior offers subcultures such as the Amish countryside.

Pennsylvania attracts visitors with its rich history, diverse culture, and varied landscapes ranging from cities to mountains. The eastern half around Philadelphia has a Mid-Atlantic character, while the western half around Pittsburgh exhibits a more Midwestern influence. The state is home to ethnic enclaves of black and Hispanic populations in major cities. Cultural attractions include the annual Little League World Series in Williamsport and the historic Steamtown National Historic Site, drawing tourists interested in both industrial heritage and natural beauty.

As of 2020, Pennsylvania has a population of 13,002,700, making it the fifth-most populous U.S. state. Its economy historically relied on steel production and manufacturing, contributing to early infrastructure development. The state has no oceanic shoreline but possesses 140 miles of waterfront along Lake Erie and the tidal Delaware River. The climate features cold, snowy winters, mild to hot humid summers, and spectacular autumn foliage, making it a varied travel destination throughout the year.