St. Clair Austin was born around 1843 in Albemarle County, Virginia. He enlisted in the 67th USCT Infantry Regiment in Tipton, Missouri, on January 12, 1864. Austin was enslaved at the time of his enlistment, and his owner Beniga Hurt filed a slave compensation claim after the war. After mustering in at Benton Barracks, Missouri, his regiment marched to Port Hudson, Louisiana, where it arrived that March. During that month, Austin was detached as a provost guard, policing and keeping order among the troops. In the summer, still stationed in Louisiana, he came down with dysentery, a deadly yet common disease among soldiers. He died on July 31, 1864, only six months after his enlistment. His regiment stayed in Louisiana until the following year, and it was mustered out in July 1865.