18. Starting its transition into a penal facility, due to its impregnability Fort Alcatraz became a prominent prison for captured Confederates during the Civil War and later held disruptive Native American dissidents
Believed to serve as an important line of defense during the American Civil War, capable of instilling order upon conflicting Union and Confederate elements within California, Alcatraz’s batteries were enlarged to a peak of 111 cannons encircling the small island. Becoming perhaps the most impregnable site in North America, designed to deter any Confederate plans to seize San Francisco, ammunition flowed like honey with 10,000 muskets and 150,000 cartridges delivered to the fort. Due to this impressive defensive capacity, Alcatraz was designated a military prison camp in August 1861.
Adding claustrophobic cells to the basement of the fort, Alcatraz became home to Confederate prisoners of war and disruptive sympathizers. Failing to see action throughout the conflict, the closest Alcatraz came to combat was in March 1863, when a group of Confederates were intercepted by the U.S. Navy en route to the island in an attempt to free the prisoners held within. Continuing to serve the function of an internment camp in the years following the Civil War, Alcatraz shifted from Confederates to Native Americans. First imprisoning Paiute Tom in 1873, dozens of indigenous persons, notably Hopi males in 1895, were incarcerated on the island.