On July 10, 1821, at four o’clock in the afternoon, Spanish gunners in the Castillo de San Marcos in St. Augustine fired a twenty-one gun salute. On the last round they lowered the royal colors and marched out of the fortification, abandoning twenty-five pieces of unserviceable artillery. Passing in front of the line of American soldiers waiting to enter the Castillo, the Spanish soldiers exchanged salutes with the representatives of the new proprietors of the Florida territory. Five days earlier, ruined Fort Matanzas, some twenty kilometers south of St. Augustine at Matanzas Inlet, had been evacuated by its three-man garrison, who abandoned two guns there. Under the terms of the Adams-Onis Treaty, negotiated two years earlier, Spain had effected the transfer of its sovereignty over East Florida to the United States of America.
Arana, Luis Rafael
"Conservation and Reutilization of the Castillo De San Marcos and Fort Matanzas,"
Florida Historical Quarterly: Vol. 65:
1, Article 6.
Available at: https://stars.library.ucf.edu/fhq/vol65/iss1/6