The 100th Ohio Infantry was organized in Toledo, Ohio July through September 1862 and mustered in for three years service under the command of Colonel John C. Groom.
The regiment was attached to 2nd Brigade, 1st Division, Army of Kentucky, Department of the Ohio, to October 1862.
2nd Brigade, 2nd Division, Army of Kentucky, to January 1863.
District of Central Kentucky, Department of the Ohio, to June 1863.
2nd Brigade, 1st Division, XXIII Corps, Army of the Ohio, to July 1863.
2nd Brigade, 4th Division, XXIII Corps, to August 1863.
1st Brigade, 3rd Division, XXIII Corps, to February 1865.
1st Brigade, 3rd Division, XXIII Corps, Department of North Carolina, to June 1865.
Ordered to Cincinnati, Ohio, September 8, thence to Covington, Ky., and duty there until October 8.
Expedition to Monticello and operations in southeastern Kentucky April 26-May 12.
(240 men captured at Telford Station while guarding railroad.)
Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church, and Allatoona Hills May 25-June 5.