The first people to occupy the area, now known as Philadelphia County, were the Native American tribes of Lenape. In 1638, the first European settlers, the Swedes and Finns, arrived, the Dutch took control of the area in 1655, and the English seized it from the Dutch in 1674. Charles II of England gave William Penn the first charter for Pennsylvania in 1681, and he divided it into three counties: Philadelphia, Chester, and Bucks. Philadelphia was made the county seat and capital of the Province of Pennsylvania in the same year.
When Philadelphia was first established as a county, it consisted of the area from the Delaware River, west between the Schuylkill River to the south, and the border of Bucks County. In 1752, Berks County was formed out of Philadelphia County, and in 1784, Montgomery County was also formed out of Philadelphia County. The current boundaries of Philadelphia County are based on these two separations. The city government of Philadelphia and the county government of Philadelphia County acted separately, and on February 2, 1854, a reform charter redefined all the boroughs, townships, and districts of Philadelphia County. This reform charter abolished the patchwork of cities, boroughs, and townships that had comprised Philadelphia County since the beginning.
In 1952, the county offices were merged with the city government eliminating the county as a government. The County of Philadelphia is still an entity within the Commonwealth of Pennsylvania, hence subject to its laws concerning counties. The population of Philadelphia County continues to grow both in numbers and ethnic diversity. It is the only First Class County, meaning it had a population of 1.5 million people or more during the last census in the Commonwealth.

William Penn, an English writer, religious thinker, and the founder of the Province of Pennsylvania, was the one who named Philadelphia County. He wanted the name Philadelphia because it means “love brotherly.” Being a religious thinker, William Penn chose the name Philadelphia because he wanted it to be a place where religious tolerance and the freedom to worship were ensured. Philadelphia also shares its name with an ancient city in Asia Minor, mentioned in the Bible’s Book of Revelation.