The regiment was attached to Fremont's Army of the West to January 1862.
5th Brigade, Army of Southwest Missouri, to March 1862.
1st Brigade, 2nd Division, Army of Southwest Missouri, to May 1862.
1st Brigade, 5th Division, Army of the Mississippi, to September 1862.
35th Brigade, 11th Division, Army of the Ohio, to October 1862.
35th Brigade, 11th Division, III Corps, Army of the Ohio, to November 1862.
2nd Brigade, 3rd Division, Right Wing, XIV Corps, Army of the Cumberland, to January 1863.
2nd Brigade, 3rd Division, XX Corps, Army of the Cumberland, to October 1863, 1st Brigade, 2nd Division, IV Corps, to April 1864.
3rd Brigade, 2nd Division, IV Corps, to June 1865.
2nd Brigade, 2nd Division, IV Corps, to August 1865.
The 15th Missouri Infantry mustered out of service at Victoria, Texas on December 25, 1865.
Curtis' Campaign in Missouri and Arkansas against Price February and March.
Moved to Cincinnati, Ohio, August 26-September 14; thence to Louisville, Ky., September 17–19.
Passage of Cumberland Mountains and Tennessee River and Chickamauga Campaign August 16-September 22.
Demonstration on Rocky Faced Ridge and Dalton May 8–13.
Advance on Dallas May 22–25, Operations on line of Pumpkin Vine Creek and battles about Dallas, New Hope Church and Allatoona Hills May 25-June 5.
Moved to New Orleans June 15–23, and to Port Lavaca, Texas, July 18–24.