17. Continuing the transformation from military fortification to a prison facility, Alcatraz Island begun incarcerating military personnel before ceasing to serve as a defensive structure entirely in the early 20th century
As a result of technological advancements, soon after the end of the Civil War Alcatraz was rendered strategically obsolete as a military fortification. Constructing a brick jailhouse in 1867, the following year Alcatraz was designated a long-term detention facility for military prisoners. Using slave labor from incarcerated military personnel and Native Americans during the 1870s and 1880s, Alcatraz Island underwent a dramatic transformation. Altering the topography of the landmass, the citadel was enlarged to offer greater accommodation for military families whilst also increasing inmate capacity.
In 1898, the outbreak of the Spanish-American War prompted an explosion in the island’s prison population, increasing from 26 to over 450. With new buildings continuously under construction to enlarge the prison, Alcatraz, miraculously suffered little to no damage during the 1906 San Francisco earthquake, served to house relocated prisoners from the decimated surrounding mainland. By 1904, with the addition of the Upper Prison, Alcatraz enjoyed a capacity in excess of 300 prisoners and, ceasing to function at all as a military fortification, was formally renamed the “Pacific Branch U.S. Military Prison” in 1907. Developing a reputation for harsh treatment and torture, its use for housing foreign prisoners of war continued until 1946 and the end of the Second World War.