Philadelphia, PA is located in Philadelphia county. The county was founded in 1682 by William Penn, and it is one of the three original counties of Pennsylvania, along with Bucks County and Chester County.
With a 2010 population of 1,526,006 people, Philadelphia County was the most populous Pennsylvania county at that time, although its land size of 134 square miles makes it the second smallest of Pennsylvania's 67 counties. In 1854, the city of Philadelphia consolidated with the county, and they now share the same borders. The act also consolidated all municipal and government offices within the city and the county.