Adams-Onis Treaty, also called the Transcontinental Treaty, was an agreement between the United States and Spain. The treaty, signed in 1819, gave the United States the area that is now Florida. In return, the United States surrendered its claim to Texas. The United States also received a strip of land that forms part of the present-day states of Alabama and Mississippi.
After the American Revolution ended in 1783, the United States controlled all the land it now occupies from the Atlantic Ocean to the Mississippi River except Spanish Florida. Indigenous (native) Americans and people who had escaped from slavery or prison took refuge in the Florida region. American troops seized two Florida forts during the First Seminole War (1817-1818). The United States demanded that Spain stop Seminole raids into Georgia or cede Florida to the United States. Spain had been weakened by conflict in Europe and faced the loss of many of its overseas territories. The Spanish could not afford to expand their military presence in Florida, so they agreed to negotiate with the Americans.
The Adams-Onis Treaty established an official western boundary for the United States. The boundary began at the mouth of the Sabine River on the Gulf of Mexico. It ran northwest to 42° north latitude and followed this line of latitude west to the Pacific Ocean. The United States agreed to Spanish claims to land south and west of the boundary. Spain approved United States claims to territory north and east of the boundary. As part of the treaty, the United States agreed to pay $5 million in claims of U.S. citizens against Spain.
The Adams-Onis Treaty was signed by Secretary of State John Quincy Adams and Luis de Onis, the Spanish minister to the United States. The document also became known as the Transcontinental Treaty. Both governments formally approved the treaty in 1821.
