East Florida
East Florida was originally a part of Spanish Florida. Under the terms of the Treaty of Paris (1763), which ended the Seven Years' War, Spain ceded all of its territory east and southeast of the Mississippi River to the Kingdom of Great Britain.
The British divided the territory into two parts, East Florida, with its capital at St. Augustine, and West Florida, with its capital at Pensacola.
Both Floridas remained loyal to Great Britain during the American Revolutionary War. Spain participated indirectly in the war as an ally of France and captured Pensacola from the British in 1781. In the Treaty of Paris (1783), which ended the war, the British ceded both Floridas to Spain.
Spain offered favorable terms for acquiring land, which attracted many settlers from the newly formed United States. There were several territorial disputes between the U.S. and Spain, some resulting in military action. An American army under Andrew Jackson invaded East Florida during the First Seminole War. Jackson's forces captured St. Mark's on April 7, 1818 and Pensacola on May 24, 1818. James Monroe's Secretary of State John Quincy Adams defined the American position on this issue. Adams accused Spain of breaking Pinckney's Treaty by failing to control the Seminoles. Faced with the prospect of losing control, Spain formally ceded all of its Florida territory to the U.S. under the Adams-Onís Treaty in 1819 (ratified in 1821) in exchange for the U.S. ceding its claims on Texas and the U.S. paying any claims its citizens might have against Spain up to $5,000,000.
In 1822, the U.S. Congress organized the Florida Territory, and in 1845, Florida was admitted as the 27th state.