Juan Ponce de Leon is credited with leading the expedition that "discovered" and claimed Florida for Spain in 1513. It is unlikely, however that he was the first European to sight Florida.

Geographical and navigational knowledge of the Caribbean region expanded as the [Spanish] empire spread. Maps and charts were drawn, informed by sea voyages that probably ranged well beyond the official version of events and discoveries that were transmitted back to Spain. The Crown, through asientos (royal contracts) awarded to the leaders of expeditions, sought to regulate these voyages and expeditions of conquest to assure the division of the spoils and future earnings. Without documented permission from the Crown, exploratory and colonizing voyages could not be legally undertaken. However, unsanctioned voyages to pillage, to capture native peoples as slaves,and locate lands for future, legal exploitation must have been ongoing. By 1530 much of the Atlantic coast of the Americas had been mapped . . .

(excerpted from Florida Indians and the Invasion from Europe, by Jerald T. Milanich, pp. 106-107)