Under the
Adams–Onís Treaty, negotiated in 1819, Spain agreed to cede Florida to the United States. Spain did not formally ratify the treaty until 1821. In March of that year,
Andrew Jackson was appointed its first territorial governor, and was given the task of overseeing the transfer of the territories of
East and West Florida from Spanish authorities. A formal ceremony was held in
St. Augustine on July 10, in which the chief United States representative was Jackson's deputy,
Robert Butler. Jackson attended the ceremony held on this plaza on July 21, in which the Spanish flag was lowered and the American flag raised. He then made a speech to the townspeople, informing them that the land was now the
Florida Territory, and that Pensacola would be its capital. As such, it was automatically included in the
National Register of Historic Places when that program began in 1966. In 1989, the plaza was listed in ''A Guide to Florida's Historic Architecture'', published by the University of Florida Press. Archaeologists, in 2002, discovered evidence of
British structures previously not known to have existed in that area. ==New Year's celebration==