Question: What treaty, signed with Spain, made the Floridas part of the U.S.?
Answer: The Adams-Onís Treaty
Secretary of State John Quincy Adams and Spanish minister Luis de Onís signed the Adams-Onís Treaty, ceding the Floridas to the United States on February 22, 1819. After the American Revolution, Spain regained control of the Florida colonies from Britain, and tensions along the border with the newly independent United States of America began almost immediately.
