Philadelphia, passionatley referred to as Philly, and known as The City of Brotherly Love from Greek: "brotherly love" from philos "loving" and adelphos "brother." Philadelphia is the fifth most populous city in the United States and the largest in population and area in the Commonwealth of Pennsylvania.

Before Europeans arrived, the Delaware Indian town of Shackamaxon was located where Philadelphia now stands, specifically the Germantown neighborhood. Although the area lay within the bounds described in the 1632 Charter of Maryland, the Calvert family's influence never reached this far north, and the first European settlers were mostly Swedes, who called it Wiccacoa. A congregation was formed in 1646 on Tinicum Island by Swedish missionary Johannes Campanius; in 1700, the group built Gloria Dei Church, also known as Old Swedes.

Philadelphia was a major center of the independence movement during the American Revolutionary War. The Declaration of Independence and US Constitution were drafted here and signed in the city's Independence Hall. Tun Tavern in the city is traditionally regarded as the location where, in 1775, the United States Marine Corps was founded.