After the battle of Chickamauga the regiment, in command of Lieutenant Colonel S. K. Bishop, was detached from its brigade by order of General Thomas, and was placed under General Smith, Chief Engineer of the Department, and performed duty as engineer troops, forming part of Engineer Brigade, and was on that duty during the engagement of Mission Ridge. It was stationed, until the 11th of June, 1864, on the north side of the Tennessee River, near Chattanooga, and was employed in building a bridge over the river, and in the erection of storehouses in Chattanooga. At the above date the regiment was ordered to Lookout Mountain, where it was engaged in building hospitals, running mills, and in the performance of the usual picket duty, until the 20th of September following, when it was relieved from further duty with the Engineer Corps. On the 27th of September the regiment left Lookout Mountain for Tullahoma, thence it proceeded to Nashville. Joining the forces under General Rosseau, it participated with them in the pursuit of the rebels under General Forrest, beyond Florence, Ala., returning to Florence on the 11th of October. On the 14th, the regiment was ordered to Chattanooga, and on the 18th to proceed to and garrison Dalton, Ga. On the 30th of October, the regiment was relieved at Dalton, and was ordered to join its corps. During the year it had traveled between 480 and 500 miles.