Pinellas County is a county located in the state of Florida. As of the 2010 census, the population was 916,542. The county is part of the Tampa–St. Petersburg–Clearwater, Florida Metropolitan Statistical Area. Clearwater is the county seat, and St. Petersburg is the largest city.
Prior to European exploration and settlement the Pinellas peninsula, like all of Tampa Bay, was inhabited by the Tocobaga Indians, who built a town and large temple mound overlooking the bay in what is now Safety Harbor. The modern site is protected and can be visited as part of the County's Philippe Park.
During the early 16th century Spanish explorers discovered and slowly began exploring Florida, including Tampa Bay. In 1528 Panfilo de Narvaez landed in Pinellas, and 10 years later Hernando de Soto is thought to have explored the Tampa Bay Area. By the early 18th century the Tocobaga had been virtually annihilated, having fallen victim to European diseases from which they had no immunity, as well as European conflicts. Later Spanish explorers named the area Punta Piñal (Spanish for "Point of Pines" or "Piney Point"). After trading hands multiple times between the British and the Spanish, Spain finally ceded Florida to the United States in 1821, and in 1823 the U.S. Army established Fort Brooke (later Tampa).
In 1834 much of west central Florida, including the Pinellas peninsula (then known simply as West Hillsborough), was organized as Hillsborough County. The very next year Odet Philippe became the first permanent, non-native resident of the peninsula when he established a homestead near the site of the Tocobaga village in Safety Harbor. It was Philippe who first introduced both citrus culture and cigar-making to Florida.
Around the same time, the United States Army began construction of Fort Harrison, named after William Henry Harrison, as a rest post for soldiers from nearby Fort Brooke during the Second Seminole War. The new fort was located on a bluff overlooking Clear Water Harbor, which later became part of an early 20th-century residential development (now historic district) called Harbor Oaks. University of South Florida archaeologists excavated the site in 1977 after Alfred C. Wyllie discovered an underground ammunition bunker while digging a swimming pool on his estate. Clearwater would later become the first organized community on the peninsula as well as the site of its first post office.
The Armed Occupation Act, passed in 1842, encouraged further settlement of Pinellas, like all of Florida, by offering 160 acres (0.65 km²) to anyone who would bear arms and cultivate the land. Pioneer families like the Booths, the Coachmans, the Marstons, and the McMullens established homesteads in the area in the years following, planting more citrus groves and raising cattle. During the American Civil War, many residents fought for the Confederate States of America. Brothers James and Daniel McMullen  were members of the Confederate Cow Cavalry, driving Florida cattle to Georgia and the Carolinas to help sustain the war effort. John W. Marston served in the 9th Florida Regiment as a part of the Appomattox Campaign. Many other residents served in other capacities. Otherwise the peninsula had virtually no significance during the war, and the war largely passed the area by.
Tarpon Springs became West Hillsborough's first incorporated city in 1887, and in 1888 the Orange Belt Railway was extended into the southern portion of the peninsula. Railroad owner Peter Demens named the town that grew near the railroad's terminus St. Petersburg in honor of his hometown. The town would incorporate in 1892. Other major towns in the county incorporated during this time were Clearwater (1891), Dunedin (1899), and Largo (1905).