East Florida was a colony of Great Britain from 1763 to 1783 and a province of the Spanish Empire from 1783 to 1821. The British gained control over Spanish Florida in 1763 as part of the Treaty of Paris that ended the Seven Years' War. Deciding that the colony was too large to administer as a single unit, British officials divided Florida into two colonies separated by the Apalachicola River; the colony of East Florida, with its capital located in St. Augustine and West Florida, with its capital located in Pensacola. East Florida was much larger and comprised the bulk of the former Spanish colony and most of the current state of Florida. It had also been the most populated region of Spanish Florida, but before control was transferred to Britain, most residents – including virtually everyone in St. Augustine – left the territory, with most migrating to Cuba.

Spanish Florida was the first major European land-claim and attempted settlement-area in northern America during the European Age of Discovery. La Florida formed part of the Captaincy General of Cuba, the Viceroyalty of New Spain, and the Spanish Empire during Spanish colonization of the Americas. While its boundaries were never clearly or formally defined, the territory was initially much larger than the present-day state of Florida, extending over much of what is now the southeastern United States, including all of present-day Florida plus portions of Georgia, South Carolina, North Carolina, Alabama, Mississippi, and the Florida Parishes of Louisiana. Spain based its claim to this vast area on several wide-ranging expeditions mounted during the 16th century. A number of missions, settlements, and small forts existed in the 16th and to a lesser extent in the 17th century; they were eventually abandoned due to pressure from the expanding English and French colonial settlements, the collapse of the native populations, and the general difficulty in becoming agriculturally or economically self-sufficient. By the 18th century, Spain's control over La Florida did not extend much beyond a handful of forts near St. Augustine, St. Marks, and Pensacola, all within the boundaries of present-day Florida.