The 115th Illinois Infantry was organized at Camp Butler and mustered in for three years service on September 13, 1862, under the command of Colonel Jesse Hale Moore.
The regiment was attached to 2nd Brigade, 3rd Division, Army of Kentucky, Department of the Ohio, to February 1862.
2nd Brigade, Baird's 3rd Division, Army of the Kentucky, Department of the Cumberland, to June 1863.
1st Brigade, 1st Division, Reserve Corps, Army of the Cumberland, to October 1863.
Moved to Cincinnati, Ohio, and Covington, Kentucky, October 4–6, 1862.
Duty at Covington, until October 20, 1862, operating against Heth's threatened attack on Cincinnati.
Repulse of Wheeler's attack on Fort Donelson, Tennessee, February 4.
Moved to Franklin, Tennessee, and pursuit of Earl Van Dorn March 5–12.
Tunnel Hill, Buzzard's Roost Gap and Rocky Faced Ridge February 23–25.
Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church, and Allatoona Hills May 25-June 5.
Ruff's Station, Smyrna Camp Ground, July 4.
Buzzard's Roost Block House October 13 (one company).
Expedition to Bull's Gap and operations in eastern Tennessee March 20-April 22.