Alcatraz Island Engineers began fortifying the island, work which continued until 1858, eventuating in Fortress Alcatraz. The island's first garrison at Camp Alcatraz, numbering about 200 soldiers and 11 cannons, arrived at the end of that year. When the American Civil War broke out in 1861, the island mounted 85 cannons (increased to 105 cannons by 1866) in casemates around its perimeter, though the small size of the garrison meant only a fraction of the guns could be used at one time. At this time it also served as the San Francisco Arsenal for storage of firearms to prevent them falling into
Alcatraz Wharf and sank in deep water off the wharf in the early 1910s. Her crew of forty-two men escaped by jumping into the bay and swimming ashore. Seismic rehabilitation of the wharf occurred in the early 2000s. The retrofit to the existing wharf and its facilities consisted of concrete demolition, excavation, and installation of tiebacks. Reinforced steel and concrete were added to a new deck. Work was also done on the deteriorated piles under the wharf deck.David Finney is the youngest person to swim the South End Rowing Club Alcatraz Swim when he swam it in 2015 at ten years old.