King of Prussia (also referred to as KOP) is a census-designated place in Upper Merion Township, Montgomery County, Pennsylvania, United States. As of the 2010 census, its population was 19,936. The community took its name in the 18th century from a local tavern named the King of Prussia Inn, which was named after King Frederick the Great of Prussia. Like the rest of Montgomery County, King of Prussia continues to experience rapid development. One of the largest shopping malls in the United States, King of Prussia, is located here. Also located here is the headquarters of the Nuclear Regulatory Commission Region I. King of Prussia is considered to be an edge city of Philadelphia, consisting of large amounts of retail and office space situated at the convergence of four highways.

Delaware County, colloquially referred to as Delco, is a county located in the U.S. state of Pennsylvania that borders Philadelphia. With a population of 566,747, it is the fifth most populous county in Pennsylvania, and the third smallest in area. The county was created on September 26, 1789, from part of Chester County, and named for the Delaware River. Its county seat is Media. Until 1850, Chester was the county seat of Delaware County and, before that, of Chester County. Delaware County is adjacent to the city-county of Philadelphia and is included in the Philadelphia–Camden–Wilmington, PA–NJ–DE–MD Metropolitan Statistical Area. Delaware County is the only county covered in its entirety by area codes 610 and 484.

Philadelphia (colloquially known simply as Philly) is a city in the Commonwealth of Pennsylvania in the United States. It is the sixth-most-populous city in the United States and the most populous city in the state of Pennsylvania, with a 2020 population of 1,603,797. It is also the second-most populous city in the Northeastern United States, behind New York City. Since 1854, the city has had the same geographic boundaries as Philadelphia County, the most-populous county in Pennsylvania and the urban core of the eighth-largest U.S. metropolitan statistical area, with over 6 million residents as of 2017. Philadelphia is also the economic and cultural center of the greater Delaware Valley along the lower Delaware and Schuylkill rivers within the Northeast megalopolis. The Delaware Valley's 2019 estimated population of 7.21 million makes it the ninth-largest combined statistical area in the United States.Philadelphia is one of the oldest municipalities in the United States. William Penn, an English Quaker, founded the city in 1682 to serve as capital of the Pennsylvania Colony. Philadelphia played an instrumental role in the American Revolution as a meeting place for the Founding Fathers of the United States, who signed the Declaration of Independence in 1776 at the Second Continental Congress, and the Constitution at the Philadelphia Convention of 1787. Several other key events occurred in Philadelphia during the Revolutionary War including the First Continental Congress, the preservation of the Liberty Bell, the Battle of Germantown, and the Siege of Fort Mifflin. Philadelphia remained the nation's largest city until being overtaken by New York City in 1790; the city was also one of the nation's capitals during the revolution, serving as temporary U.S. capital while Washington, D.C. was under construction. In the 19th and 20th centuries, Philadelphia became a major industrial center and a railroad hub. The city grew due to an influx of European immigrants, most of whom initially came from Ireland and Germany—the two largest reported ancestry groups in the city as of 2015. Later immigrant groups in the 20th century came from Italy (Italian being the third largest European ethnic ancestry currently reported in Philadelphia) and other Southern European and Eastern European countries. In the early 20th century, Philadelphia became a prime destination for African Americans during the Great Migration after the Civil War. Puerto Ricans began moving to the city in large numbers in the period between World War I and II, and in even greater numbers in the post-war period. The city's population doubled from one million to two million people between 1890 and 1950. The Philadelphia area's many universities and colleges make it a top study destination, as the city has evolved into an educational and economic hub. As of 2019, the Philadelphia metropolitan area is estimated to produce a gross metropolitan product (GMP) of $490 billion. Philadelphia is the center of economic activity in Pennsylvania and is home to five Fortune 1000 companies. The Philadelphia skyline is expanding, with a market of almost 81,900 commercial properties in 2016, including several nationally prominent skyscrapers. Philadelphia has more outdoor sculptures and murals than any other American city. Fairmount Park, when combined with the adjacent Wissahickon Valley Park in the same watershed, is one of the largest contiguous urban park areas in the United States. The city is known for its arts, culture, cuisine, and colonial history, attracting 42 million domestic tourists in 2016 who spent $6.8 billion, generating an estimated $11 billion in total economic impact in the city and surrounding four counties of Pennsylvania. Philadelphia has also emerged as a biotechnology hub.Philadelphia is the home of many U.S. firsts, including the nation's first library (1731), hospital (1751), medical school (1765), national capital (1774), university (by some accounts) (1779), stock exchange (1790), zoo (1874), and business school (1881). Philadelphia contains 67 National Historic Landmarks and the World Heritage Site of Independence Hall. The city became a member of the Organization of World Heritage Cities in 2015, as the first World Heritage City in the United States.

Kennett Square is a borough in Chester County, Pennsylvania, United States. It is known as the Mushroom Capital of the World because mushroom farming in the region produces over 500 million pounds of mushrooms a year, totaling half of the United States mushroom crop. To celebrate this heritage, Kennett Square has an annual Mushroom Festival, where the town shuts down to have a parade, tour mushroom farms, and buy and sell food and other goods. It is also home to the corporate headquarters of Genesis HealthCare which administers elderly care facilities. Located in the Delaware Valley, Kennett Square is considered a suburb of both Philadelphia, Pennsylvania and Wilmington, Delaware. The local high school is Kennett High School. Its population was 6,072 at the 2010 census. It is also the birthplace of the sister of the 46th and current president of the United States, Valerie Biden.