The One Hundred and Fifty-fifth Infantry Illinois Volunteers was organized at Camp Butler, Ill., by Colonel Gustave A. Smith, and mustered in February 28, 1865, for one year. On March 2, the Regiment -904 strong- moved, via Louisville and Nashville to Tullahoma, Tenn., and reporting to General Milroy, was assigned to the command of Brevet Brigadier General Dudley. On June 17, the Regiment was divided into detachments of twenty or thirty men each, and assigned to guard duty on the Nashville and Chattanooga Railroad, occupying the block houses from Nashville to Duck River, a distance of fifty miles.

On September 4, the Regiment was mustered out of service, and moved to Camp Butler, Ill., where it received final pay and discharge.