There are 48 US Post Offices in Philadelphia County serving a total of 1,627,980 residents equating to 33,916 residents per post office. It's estimated that approximately 2,598,438 packages are handled across the 48 county post offices annually. Philadelphia County is a county located in the commonwealth of Pennsylvania. At the 2010 census, the population was 1,526,006, making it the most populous county in the state, despite being the second smallest county in the state by land area. Philadelphia County is one of the three original counties, along with Chester and Bucks counties, created by William Penn in November 1682. Since 1854, the county has been coterminous with the city of Philadelphia, which also serves as its seat. It is the most populous county in the United States coterminous with a municipality. Philadelphia County is the heart of the Philadelphia-Camden-Wilmington, PA-NJ-DE-MD (Delaware Valley) Metropolitan Statistical Area. The Metropolitan Area ranks 7th most populous in the United States."