United States territorial acquisitions
West Florida was declared to be a U.S. possession in 1810 by President James Madison after the territory had declared its independence from Spain. Madison ordered the U.S. Army to take control. Six weeks later, the army entered and occupied the capital, St. Francisville, putting an end to the republic after 74 days of independence. Spain did not relinquish its claim to sovereignty (see West Florida Controversy) until ratification of the Adams–Onís Treaty. General Andrew Jackson personally accepted the delivery of West Florida from its Spanish governor on July 17, 1821.
St. Augustine, Florida
During the Second Spanish period (1784-1821) of Florida, Spain was dealing with invasions of the Iberian peninsula by Napoleon's armies in the Peninsular War, and struggled to maintain a tenuous hold on its territories in the western hemisphere as revolution swept South America. The royal administration of Florida was neglected, as the province had long been regarded as an unprofitable backwater by the Crown. The United States, however, considered Florida vital to its political and military interests as it expanded its territory in North America, and maneuvered by sometimes clandestine means to acquire it. The Adams–Onís Treaty, negotiated in 1819 and ratified in 1821, ceded Florida and St. Augustine, still its capital at the time, to the United States.