Pinellas County lies on Florida's West Coast, a 280-square mile peninsula bordered by the Gulf of Mexico and Tampa Bay. The peninsula is 38 miles long and 15 miles wide.

The word Pinellas is derived from the Spanish words Punta Pinal, which translated means "point of pines." It was how its discoverer, Panfilo de Narvaez, described it in 1528. Explorers from Europe were probably the first outsiders in this area, but the first inhabitants were Native Americans and Indian shell mounds attest to that. One shell mound is located at Pinellas County's Philippe Park in Safety Harbor.

In 1912 the population was a little over 13,000. It is now considered the most densely populated county in the state.