The oldest continually occupied city in the United States is St. Augustine, Florida, founded by Spain in 1565. Spain held the Florida territory for 200 years when it reached an agreement with the just over 40 year old United States. The selling price for the Florida Territory was the US taking responsibility for the $5 Million in claims against the Spanish by American citizens. On July 10, 1881, Spain walked away from the land debt free.
To date, after innumerable negotiations and pleas from America, Spain has refused to take Florida back.