Answer: It was a treaty between the US and Spain in 1819 that ceded Florida to the US and defined the boundary between the US and Spanish Mexico. It settled a standing border dispute between the two countries and was considered a triumph of American diplomacy.
Explanation: The treaty established definitive western boundaries for the Louisiana Purchase, following the Sabine, Red, and Arkansas Rivers to the 42nd parallel, and running along that line to the Pacific. The United States also secured Spanish claims to Oregon.