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.
West Florida Controversy
Previous to May, 1803, U.S. envoy Robert Livingston had contended that West Florida formed no part of Louisiana. However, the ambiguous third article of the treaty of St. Ildefonso lent itself to his purpose, although he had to adopt an interpretation that France had not asserted nor Spain allowed. Chambers arrives at what he calls the key to Mr. Livingston's sudden change of conviction concerning West Florida: "It had been and was the desire of the United States to acquire West Florida and the Island of Orleans. [James] Monroe had assented to the purchase of Louisiana instead. If Livingston could formulate a reasonable theory upon which the United States could base a claim to West Florida the glory would be his and his alone."