Hillsborough County is a county located in the U.S. state of Florida. Its county seat is Tampa. Hillsborough County is the largest county in the Tampa-St. Petersburg-Clearwater Metropolitan Area. This County has an unusually high number of communities that are unincorporated, and a high percentage of people living here. Hillsborough County has a total area of approximately 3,279 square miles of which 83% is land and 17% water. As of the 2000 census, there were 998,948 people, 391,357 households, and 255,164 families residing in Hillsborough County, FL.