Maritime history of Florida
Spain ceded Florida to the United States as part of the Adams–Onís Treaty of 1819, and Florida became a U.S. territory in 1821. Coastal trade with other markets continued to expand and towns like Jacksonville, Pensacola and Tampa became important ports. After becoming a U.S. territory, the federal government began building a series of lighthouses as aids to navigation along the coasts of Florida to mark dangerous headlands, shoals, bars and reefs.
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.