Florida Sold to U.S.: Expansion Solidified

Spain sold a territory it could no longer control, and the United States gained a peninsula that would become the nation's third-most-populous state. The Adams-Onis Treaty, signed on February 22, 1819, transferred all of Spanish Florida to the United States for $5 million — not paid to Spain, but used to settle claims by American citizens against the Spanish government. In effect, the United States acquired Florida for free. The transfer had been inevitable for years. Spain's grip on Florida had weakened steadily as its Latin American colonies revolted and its European position deteriorated after the Napoleonic Wars. The territory had become a haven for runaway slaves, pirates, and Seminole warriors who raided American settlements in Georgia and retreated across the border. In 1818, Andrew Jackson invaded Florida without authorization, seized Spanish forts at St. Marks and Pensacola, and executed two British subjects he accused of aiding the Seminoles. Rather than provoking war, Jackson's incursion proved Spain's inability to govern the territory. Secretary of State John Quincy Adams, considered the finest diplomat of his generation, negotiated the treaty with Spanish minister Luis de Onis. The agreement did more than transfer Florida. It established the western boundary of the Louisiana Purchase along the Sabine, Red, and Arkansas rivers to the Continental Divide and then along the 42nd parallel to the Pacific, with Spain ceding all claims to the Oregon Country. Adams later called it "the most important day of my life" — a remarkable statement from a man who would become president. The treaty reshaped the continent. It eliminated European sovereignty from the Gulf Coast east of New Orleans, secured American access to the Gulf of Mexico, and extended U.S. territorial claims to the Pacific Ocean for the first time. Florida's acquisition also intensified the national crisis over slavery, as Southern politicians pushed for its rapid development as slave territory.