Adams-Onís Treaty (1819)

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The Adams-Onís Treaty, signed on February 22, 1819, was a significant agreement between the United States and Spain. It resolved long-standing border disputes between the two nations, marking a crucial milestone in U.S. expansion. The treaty involved Spain ceding Florida to the United States and establishing the Sabine River as the boundary between U.S. territory and Spanish Texas. This agreement also led to the U.S. relinquishing claims on parts of Spanish Texas west of the Sabine River and other Spanish territories, under the terms of the Louisiana Purchase. The treaty further defined U.S. claims through the Rocky Mountains to the Pacific Ocean, including the Oregon Territory. The U.S. agreed to pay $5 million to settle American citizens' claims against Spain. Although ratified in 1821, the treaty's full effect was short-lived due to Mexico's independence from Spain. The border established by the treaty was later recognized in the Treaty of Limits between Mexico and the U.S. in 1828. This treaty marked a significant success for U.S. diplomacy under Secretary of State John Quincy Adams and played a pivotal role in shaping U.S. territorial expansion.