Philadelphia is the county seat of Philadelphia. Along with Bucks County and Chester County, the county was formed in 1682 by William Penn and is one of the three founding counties of Pennsylvania.
Philadelphia County, with a population of 1,526,006 people in 2010, was the most populated Pennsylvania county at the time, while being the second smallest of Pennsylvania’s 67 counties with a land area of 134 square miles. The city of Philadelphia merged with the county in 1854, and the two currently share the same borders. All municipal and government offices inside the city and county were also consolidated by the act.