Pinellas County is a county located in the U.S. state of Florida. Its county seat is Clearwater and its largest city is St. Petersburg. Pinellasis one of the three Counties that comprises the Tampa-St.Petersburg-Clearwater metro area, often called the Tampa Bay area. It is the most densely populated county in Florida, 3,292/miČ Pinellas County has a total area of approximately 1,574 square miles of which 46% is land and 54% water. As of the 2000 census, there were 921,482 people, 414,968 households, and 243,171 families residing in Pinellas County, FL.