Historians credit Juan Ponce de Leon, the first governor of the Island of Puerto Rico, with the discovery of Florida in 1513. While on an exploratory trip in search of the fabled Bimini he sighted the eastern coast of Florida on Easter Sunday, which fell on March 27 that year. Ponce de Leon claimed Florida for the Spanish Crown and named it Florida after the Easter season, known in Spanish as PASCUA FLORIDA. This newly claimed territory extended north and west to encompass most of the known lands of the North American continent that had not been claimed by the Spanish in New Spain (Mexico and the Southwest).

In the following half century, the government of Spain launched no less than six expeditions attempting to settle Florida; all failed. In 1564 French Huguenots (Protestants) succeeded in establishing a fort and colony near the mouth of the St. Johns River at what is today Jacksonville. This settlement posed a threat to the Spanish fleets that sailed the Gulf Stream beside the east coast of Florida, carrying treasure from Central and South America to Spain. As Don Pedro Menéndez de Avilés was assembling a fleet for an expedition to Florida, the French intrusion upon lands claimed by Spain was discovered. King Philip II instructed Menéndez, Spain's most capable admiral, to remove the French menace to Spain's interests.