On December 27, 1860, one week after South Carolina
seceded from the
Union, the fort was surrendered to South Carolina (S.C.)
militia by its small U.S. Army garrison, which retired to Fort Sumter to join
Major Robert Anderson. Castle Pinckney became the first
Federal military installation seized forcefully by a
Southern state government. Three days later, the
Union's
Charleston Arsenal also fell to S.C. forces. After the subsequent
Confederate attack on Fort Sumter, the Charleston
Zouave Cadets garrisoned Castle Pinckney. One hundred and fifty-four
Union Army prisoners of war (120 enlisted, 34 officers) captured during the
First Battle of Bull Run and previously incarcerated at Ligon's Prison arrived at Charleston on September 10, 1861, and were kept at the Charleston City Jail until the lower
casemates of Castle Pinckney were converted into cells. According to the
Charleston Mercury, Richmond officials had selected "chiefly from among those who have evidenced the most insolent and insubordinate disposition." On September 18, prisoners from the 11th NY Fire
Zouaves, 69th NY ("Irish") Regiment, 79th NY Regiment, and 8th Michigan Infantry were transferred to Castle Pinckney. They were allowed to wander during the day and were confined to cells only at night. The Castle quickly proved to be too small and inadequate, however, for permanent confinement; the prisoners were transferred back to the Charleston City Jail on October 31, 1861, after only six weeks. After the prisoners were removed, the fort was strengthened with earthen embankments and with additional
mortars and
Columbiads on the
barbette tier. On December 12, the prisoners were transferred back to the island, following a fire which had burned a large section of Charleston and damaged the jail. They remained for just over a week with many sleeping on the inner parade ground before being transferred. ==Post Civil War and disuse==