Whole plate ambrotype. (Occasional scratches to lacquer, only visible when held to light.) Housed in walnut frame (opening refinished). 

An important scene, and possibly one of the only hard images of Fort Marion (Castillo de San Marcos). The oldest masonry fort in the continental United States with construction beginning in 1672, the fort was renamed Fort St. Mark when the British gained control of Florida in 1763. When Florida was ceded to the United States in 1821, it was renamed again to Fort Marion. 

Florida seceded in January 1861 and Federal troops withdrew from the fort, leaving a caretaker, Ordinance Sergeant Henry Douglas. When Confederate troops marched on Fort Marion, Douglas handed over the keys once he received a signed receipt. During the early war, St. Augustine was an important base of operations for blockade runners and a high priority for the Union Navy. On 11 March 1862, St. Augustine and the fort were reoccupied by Federal forces when acting mayor Cristobal Bravo surrendered to US Navy fleet commander Christopher Raymond Perry Rodgers. After the War, the fort was used as a military prison, primarily for Native Americans. 

This image, showing artillery pieces and stacked round shot, was possibly taken during the Confederate occupation, or it may have been taken pre-war.