Edgar D. Swain served as lieutenant colonel of the 42nd Illinois Infantry, a regiment that fought at Island No. 10, Stones River, Chickamauga, Missionary Ridge, the Atlanta Campaign, and the battles of Franklin and Nashville. Regimental sources confirm his rank and that he mustered out with the regiment in December 1865, but do not record details of his wounds, promotion timeline, or personal vital statistics, which could not be independently verified.