Florida was the first part of what is now the continental United States to be visited by Europeans. The earliest known European explorers came with the Spanish conquistador Juan Ponce de León. According to the "500TH Florida Discovery Council Round Table", on March 3, 1513, Ponce de Leon, organized and equipped three ships which began an expedition (with a crew of 200, including women and free blacks), departing from Punta Aguada Puerto Rico. Puerto Rico was the historic first gateway to the discovery of Florida, which opened the doors to the advanced settlement of the U.S. They introduced Christianity, cattle, horses, sheep, the Spanish language and more to Florida.[11][broken citation]

Ponce de León spotted the peninsula on April 2, 1513. According to his chroniclers, he named the region La Florida ("flowery land") because it was then the Easter Season, known in Spanish as Pascua Florida (roughly "Flowery Easter"), and because the vegetation was in bloom.[12] Juan Ponce de León may not have been the first European to reach Florida, however; reportedly, at least one indigenous tribesman whom he encountered in Florida in 1513 spoke Spanish.[13] From 1513 onward, the land became known as La Florida. After 1630, and throughout the 18th century, Tegesta (after the Tequesta tribe) was an alternate name of choice for the Florida peninsula following publication of a map by the Dutch cartographer Hessel Gerritsz in Joannes de Laet's History of the New World.[14][15][16]

The horse, which the natives had eaten into extinction 10,000 years ago,[17] was reintroduced into North America with the European explorers and into Florida in 1538.[18] As the animals were lost or stolen, they began to become feral.

Over the following century, both the Spanish and French established settlements in Florida with varying degrees of success. In 1559, Don Tristán de Luna y Arellano established a colony at present-day Pensacola, one of the first European attempts at settlement in the continental United States. It was abandoned by 1561 due to hurricanes, famine, and warring tribes, and the area was not re-inhabited until the 1690s.

French Protestant Huguenots founded Fort Caroline in modern-day Jacksonville in 1564. The following year, the Spanish colony of St. Augustine (San Agustín) was established, and forces from there conquered Fort Caroline that same year. The Spanish maintained tenuous control over the region by converting the local tribes, briefly with Jesuits and later with Franciscan friars.

The area of Spanish Florida diminished with the establishment of English colonies to the north and French colonies to the west. The English weakened Spanish power in the area by supplying their Creek and Yamasee allies with firearms and urging them to raid the Timucuan and Apalachee client-tribes of the Spanish. The English attacked St. Augustine, burning the city and its cathedral to the ground several times, while the citizens hid behind the walls of the Castillo de San Marcos.

Florida attracted numerous Africans and African Americans from the southern British colonies in North America who sought freedom from slavery. Once in Florida, the Spanish Crown converted them to Roman Catholicism and gave them freedom. Those freedmen settled in a community north of St. Augustine, called Gracia Real de Santa Teresa de Mose, the first free black settlement of its kind in what became the United States. Many of those slaves were also welcomed by Creek and Seminole Native Americans, who had established settlements in the region at the invitation of the Spanish government.

Great Britain gained control of Florida and other territory diplomatically in 1763 through the Peace of Paris following its defeat of France in the Seven Years' War, and exchanges with Spain of possessions. The British divided their new acquisitions into East Florida, with its capital at St. Augustine, and West Florida, with its capital at Pensacola.

Britain tried to develop the Floridas through the importation of immigrants for labor, but this project ultimately failed. Spain received both Floridas after Britain's defeat by the American colonies and the subsequent Treaty of Versailles in 1783, continuing the division into East and West Florida. They offered land grants to anyone who settled in the colonies, and many Americans moved to them.

After settler attacks on Indian towns, Seminole Indians based in East Florida began raiding Georgia settlements, purportedly at the behest of the Spanish. The United States Army led increasingly frequent incursions into Spanish territory, including the 1817–1818 campaign against the Seminole Indians by Andrew Jackson that became known as the First Seminole War. Following the war, the United States effectively controlled East Florida.