It was organized at Peoria in September 1862 and garrisoned places in Kentucky until Spring 1863.

Beginning in April 1863, the regiment served as mounted infantry during the Knoxville campaign, before being dismounted in February 1864.

The 112th Illinois Infantry was organized at Peoria, Illinois, and mustered in for three years service on September 20, 1862 under the command of Colonel Thomas Jefferson Henderson.

The regiment was attached to 1st Brigade, 2nd Division, Army of Kentucky, Department of the Ohio, to January 1863.

3rd Brigade, District of Central Kentucky, Department of the Ohio, to April 1862.

2nd Brigade, District of Central Kentucky, Department of the Ohio, to June 1863.

1st Brigade, 1st Division, XXIII Corps, Army of the Ohio, to August 1863.

2nd Brigade, 4th Division, XXIII Corps, to November 1863.

3rd Brigade, 3rd Division, XXIII Corps, Army of the Ohio, to February 1865, and Department of North Carolina to June 1865.

The 112th Illinois Infantry mustered out of service at Greensboro, North Carolina June 20, 1865, and was discharged at Chicago on July 7, 1865.

Moved to Danville, Kentucky, March 21; then to Nicholasville, Camp Dick Robinson, Lancaster, Crab Orchard, Stanford, and Milledgeville, Kentucky.

Operations against Pegram's forces in southeastern Kentucky April 26-May 12.

Saunders' Raid in eastern Tennessee June 14–24 (detachment).

Operations in eastern Kentucky against Scott July 26-August 6.

Burnside's Campaign in eastern Tennessee August 16-October 16.

Bend of Chucky Road, near Dandridge, January 16, 1864.

Moved to Camp Nelson, Kentucky, April 6, then to Knoxville, Tennessee, arriving May 3.

Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church, and Allatoona Hills May 25-June 5.

Operations about Marietta and against Kennesaw Mountain June 10-July 2.

Pursuit of Hood to the Tennessee River December 17–29.

Movement to Washington, D.C., then to Fort Fisher, North Carolina, January 18-February 9.