St. Petersburg is a city in Pinellas County, Florida, United States. As of the 2013 census estimate, the population was 249,688, making St. Petersburg the 4th most populous city in the state of Florida and the largest city in Florida that is not a county seat (the city of Clearwater is the county seat). St. Petersburg is the second largest city in the Tampa Bay Area, after Tampa, composed of roughly 2.8 million residents, making it the second largest Metropolitan Statistical Area in the state.