There are 26 US Post Offices in Pinellas County serving a total of 480,109 residents equating to 18,466 residents per post office. It's estimated that approximately 766,308 packages are handled across the 26 county post offices annually. Pinellas County is a county located in the state of Florida. As of the 2010 census, the population was 916,542. Its county seat is Clearwater, and its largest city is St. Petersburg. Pinellas County is included in the Tampa\u2013St. Petersburg\u2013Clearwater, Florida Metropolitan Statistical Area.