Philadelphia is the fifth most populous city in the United States and is one of the oldest and most historically significant cities in the United States. During part of the 18th century, the city was the second capital and most populous city of the then country. At that time, it eclipsed Boston and New York City in political and social importance, with Benjamin Franklin playing an extraordinary role in Philadelphia's rise.

Philadelphia is a planned city, founded and developed in 1682 by William Penn, a Quaker. The city's name means "brotherly love" in Greek. Penn hoped that the city, as the capital of his new colony founded on principles of freedom and religious tolerance, would be a model of this philosophy. Penn allowed for the construction of alleyways and open spaces, in the hope of controlling fires and disease, then a common problem in older European cities.