Organized at Chicago in August, 1862, by the railroad companies in the State of Illinois. Captain John Christopher, Sixteenth United States Infantry, was selected for the colonelcy, but as he never reported for duty the command devolved upon Lieutenant-Colonel Hotchkiss, who was promoted after a few months to the vacant position. The regiment was ordered into Kentucky, September 4th, where it was assigned to Cruft's Divi sion of General Nelson's Army of Kentucky. At Stone's River, its first battle, it fought in Willich's (1st) Brigade, Johnson's (2d) Division, McCook's Corps; loss, 10 killed, 46 wounded, and 94 captured or missing; at Liberty Gap, it lost 3 killed and 10 wounded; at Chickamauga, 14 killed, 88 wounded, and 30 missing. In the latter engagement, Lieutenant-Colonel Duncan J. Hall, who was then in command of the Eighty-ninth, and four line officers were killed. Upon the reörganization of the Army of the Cumberland, in October, 1863, Willich's Brigade was placed in Wood's (3d) Division, Fourth Corps, in which it fought at Missionary Ridge, the regiment losing in that battle, 4 killed, and 30 wounded. While on the Atlanta campaign, this brigade took the lead in the bloody assault at Pickett's Mills, May 27th, in which the regiment sustained a loss of 24 killed, 102 wounded, and 28 missing; total, 154. Upon the evacuation of Atlanta, Sherman and the main army marched un molested through Georgia, while the Fourth and Twenty-third Corps were engaged in a bloody campaign with Hood in Middle Tennessee. The Eighty-ninth participated in this fighting, its loss at Nashville being quite heavy in proportion to the small number engaged; its casualties in that action were 4 killed and 16 wounded. The regiment was mustered out at Nashville, June 10, 1865, and the recruits with unexpired terms (202 in number) were left in the field and transferred to the Fifty-ninth Illinois Infantry.