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 Citadel coves and bay. In 1882, the citadel was enlarged to provide more accommodation for the families of the military officers working on Alcatraz. Between 1873 and 1895, 32 Native Americans were imprisoned at the citadel on Alcatraz, including 19 Hopi men held in captivity there between January and August 1895 after being transferred from Fort Defiance. The island continued to develop in the 1880s and in 1898 the population of Alcatraz increased dramatically from 26 to over 450 due to the Spanish–American War and placed a demand for new buildings. The original barracks evolved into Building 64 in 1905. The