A state of the southeast United States bordering on the Atlantic Ocean and the Gulf of Mexico. It was admitted as the 27th state in 1845. The peninsula was explored by Juan Ponce de León in 1513 and became the center of a Spanish settlement that included the southeast part of the present-day United States. Spain finally ceded the area in 1819. Tallahassee is the capital and Jacksonville the largest city. Population: 18,300,000..