James Caswell Knox was born in North Carolina in May 1834, the second son of Hosea Knox and Clementina Evans. The family moved from North Carolina to Greensfork Township, Randolph County, Indiana, between 1835 and 1839. On February 15, 1855, Knox married 20-year old Catharine Armstrong, daughter of Samuel and Margaret Armstrong. Catharine's family had emigrated from Ireland between 1835 and 1843.
The couple had one son, Columbus C. Knox, who was born about 1856 and apparently died before James entered the service, as the child is never mentioned in correspondence. On February 7, 1865, James enlisted as a private in Company I, 147th Indiana Infantry, at about the time that the regiment was forming. The regiment mustered at Indianapolis, Indiana, March 9, 1865, and left the state for Harper's Ferry, West Virginia, March 11. It was attached to the 1st Brigade, 2nd Provisional Division, Army of the Shenandoah. The regiment saw little action as the war ended shortly after it arrived at Harper's Ferry. James was promoted to sergeant April 1, 1865. While the regiment was awaiting orders to muster out, James became ill and was eventually sent to Clarysville U.S. Hospital in Maryland, where he was discharged on July 17, 1865. James and Catharine lived out their days in Greensfork Township, where James worked as a painter and cobbler. He died about 1911, as his wife Catharine applied for a widow's pension in October of that year.