What was the Adams-Onís Treaty?

On 22 February, 1819, Adams and Onís signed the treaty they’d negotiated—an event Adams would later describe as “the most important event of my life.” The U.S. had acquired the last piece of West Florida, all of East Florida (together, these would be known now as Florida Territory), plus an entire transcontinental border with the Spanish Empire. In addition, Spain relinquished claims it had once had to the Pacific Northwest. In return, Spain received $5 million from the U.S. (this sum actually represented claims that Americans had against the Spanish government in Florida, which the U.S. government agreed to pay), special trade privileges in Pensacola and St. Augustine, and, most importantly, U.S. recognition of Texas (west of the Sabine River) as a Spanish jurisdiction. This last point was hotly contested by some in Congress, notably Henry Clay, who had hoped that Spain might give Texas up entirely. This first major bid for Texas failed. On the Spanish side, hopes that the Americans might disavow the various Latin American revolutions then rocking their empire also proved vain.

It took two years for both governments to complete the treaty ratification process, but by February 1821, the “Transcontinental Treaty” had been made official.