Answer: Transcontinental Treaty
Explanation: The U.S. gained Florida through the Transcontinental Treaty. It is also known as the Adams–Onís Treaty (Spanish: Tratado de Adams-Onís) of 1819. It can also be called the Florida Purchase Treaty, or the Florida Treaty. This was a treaty between the US and Spain in 1819 that gave Florida to the US and made the boundaries between US and New Spain.