Philadelphia County is the most populous county in the U.S. state of Pennsylvania.As of 2019, Philadelphia County was home to an estimated population of 1,584,064 residents. The county is the second smallest county in Pennsylvania by land area, after Montour County.Philadelphia County is one of the three original counties, along with Chester and Bucks counties, created by …

This is intended to be a complete list of the Pennsylvania state historical markers in Philadelphia County, as placed by the Pennsylvania Historical and Museum Commission (PHMC).. As of 2021, there were 321 combined Roadside (larger) and City (narrower) markers affixed on posts and Plaque markers affixed to buildings or structures in Philadelphia County, Pennsylvania, which …