On Feb. 22, 1819, U.S. Secretary of State John Quincy Adams and Spanish minister Do Luis de Onis signed the Florida Purchase Treaty, in which Spain agreed to cede Florida to the United States. In exchange, the U.S. government assumed approximately $5 million of claims by U.S. citizens against Spain.
Spanish colonization of Florida began in 1565. In the 17th century, after a period of relative stability, Spanish colonists came under attack from Native Americans and English colonists to the north. Spain subsequently lost Florida to the British following Spain's involvement in the French and Indian War. After 20 years of British rule, however, Florida was returned to Spain as a condition of the second Treaty of Paris, which ended the American Revolution in 1783.
Spain struggled to hold on to Florida in the period following American independence, as boundary disputes developed with the United States. After years of tough negotiations, the signing of the Florida Purchase Treaty was seen as a major diplomatic achievement for John Quincy Adams. Formal U.S. occupation of Florida began in 1821, and General Andrew Jackson was appointed military governor. Florida was organized as a U.S. territory in 1822 and admitted into the union as a slave state in 1845.