The 81st Indiana Infantry was organized and mustered in at New Albany, Indiana for a three-year enlistment on August 29, 1862, under the command of Colonel William W. Caldwell.
The regiment was attached to 32nd Brigade, 9th Division, Army of the Ohio, September 1862.
32nd Brigade, 9th Division, III Corps, Army of the Ohio, to November 1862.
3rd Brigade, 1st Division, Right Wing, XIV Corps, Army of the Cumberland, to January 1863.
3rd Brigade, 1st Division, XX Corps, Army of the Cumberland, to March 1863.
1st Brigade, 1st Division, IV Corps, Army of the Cumberland, to June 1865.
The 81st Indiana Infantry mustered out of service at Nashville, Tennessee, on June 13, 1865.
March to Nashville, Tennessee, October 16-November 7, and duty there until December 26.
Passage of the Cumberland Mountains and Tennessee River and Chickamauga Campaign August 16-September 22.
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.