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.
History of slavery in Florida
As Florida had become a burden to Spain, which could not afford to send settlers or garrisons, the Crown decided to cede the territory to the United States. It accomplished this through the Adams–Onís Treaty, which took effect in 1821.