Spanish Florida was established in 1513, when Juan Ponce de León claimed peninsular Florida for Spain during the first official European expedition to North America. This claim was enlarged as several explorers (most notably Pánfilo Narváez and Hernando de Soto) landed near Tampa Bay in the mid-1500s and wandered as far north as the Appalachian Mountains and as far west as Texas in largely unsuccessful searches for gold.^[14] The presidio of St. Augustine was founded on Florida's Atlantic coast in 1565; a series of missions were established across the Florida panhandle, Georgia, and South Carolina during the 1600s; and Pensacola was founded on the western Florida panhandle in 1698, strengthening Spanish claims to that section of the territory.

Spanish control of the Florida peninsula was much facilitated by the collapse of native cultures during the 17th century. Several Native American groups (including the Timucua, Calusa, Tequesta, Apalachee, Tocobaga, and the Ais people) had been long-established residents of Florida, and most resisted Spanish incursions onto their land. However, conflict with Spanish expeditions, raids by the Carolina colonists and their native allies, and (especially) diseases brought from Europe resulted in a drastic decline in the population of all the indigenous peoples of Florida, and large swaths of the peninsula were mostly uninhabited by the early 1700s. During the mid-1700s, small bands of Creek and other Native American refugees began moving south into Spanish Florida after having been forced off their lands by South Carolinan settlements and raids. They were later joined by African-Americans fleeing slavery in nearby colonies. These newcomers – plus perhaps a few surviving descendants of indigenous Florida peoples – eventually coalesced into a new Seminole culture.