February 22, 1819, was, John Quincy Adams recorded in his diary, “perhaps the most important day of my life.” On that day, the United States finalized a momentous treaty with Spain that acquired Florida for the United States and settled a border with Spain’s North American provinces that reached across the continent to give the United States a piece of Oregon on the Pacific Ocean. The agreement was known officially as the Treaty of Amity, Settlement, and Limits Between the United States of America and His Catholic Majesty. Today, it’s more commonly called the Transcontinental Treaty, to emphasize its geographic scope, or it’s known as the Adams–Onís Treaty, after its two architects, Secretary of State Adams and Spanish minister plenipotentiary Luis de Onís.