"There is a Mote Round it of 30. feet wide & a draw Bridge of about 15 feet long, they draw every Night & lett it down in the Morning...."
Ironically enough, before the eighth anniversary of the Fernández plaque, the _alerta_ of the Spanish sentry was replaced by a challenge in English, for in 1763 the diplomats gave Florida and the castillo to England.
It was some years before the English put their ineffaceable mark on the fort, but in the summer after Lexington and Concord they went to work. The gates were repaired and the well in the courtyard, become brackish, was re-dug. A new palisade for the covered way was built and the glacis--the encircling earthwork--repaired. Several of the high arched rooms were given a second floor, in a sense a second story, in order to make more room for long bunkshelves, for St. Augustine was regimental headquarters and many red-coated troops were quartered in the Castle of St. Mark. Within the safety of the thick walls were stored the arms that went to ranger, regular, and Indian ally alike for repeated use against the rebellious colonials to the north. And a goodly number of those colonials and their friends languished in the damp prison of the castle.
Those were exciting times, but they were only an interlude. The Union Jack was not the flag for the fort. When the Spanish came back by the terms of the 1783 treaty, Florida had lost its old importance to the empire, even though San Marcos remained a bulwark that American advances never quite reached. For the Spanish, awaiting the manifest destiny that was to bring Florida into the union of the United States of America, there was little to do but maintenance work, such as repairs to the bridges, a new pine stairway for San Carlos tower, a bench for the criminals in the prison. In 1785 Mariano de la Rocque designed a beautiful entrance for the chapel doorway. It was built, only to crumble slowly away like the Spanish hold on Florida.
When at last the red and gold ensign of Spain fluttered down under the thunderous salute of the old smoothbores, to be replaced by the 23-star flag of 1821, the aging fort was obsolete--already a historical relic. Fortunately for its preservation, the strategy of St. Augustine Harbor was gone. The young republic built powerful seacoast forts from Maine to Texas but the only concession to this one-time capital of the southeast was the building of a water battery in the moat east of the fort and the mounting of a few big guns on the bastions. The fort remained unchanged, except in name. For more than 150 years St. Mark had been the patron saint of this defense. The Americans chose to honor Gen. Francis Marion, the Revolutionary leader and son of the very colony against which San Marcos had been built. Spanish Castillo de San Marcos became American Fort Marion. (Legislation enacted by Congress in June 1942 restored the original name of Castillo de Marcos.)