Organized at Springfield, Ill., in September, 1861. It was stationed at Cairo until February, 1862, when it embarked on the expedition against Forts Henry and Donelson, having been assigned to W. H. Wallace's Brigade of McClernand's Division. In the action at Fort Donelson, it lost 8 killed, 31 wounded, and 3 missing; Lieutenant-Colonel Thomas H. Smith was among the killed. At Shiloh, it lost 18 killed, 112 wounded, and 3 missing. The regiment was engaged in the Siege of Corinth, after which, in June, 1862, it was ordered to Bethel, Tenn., on garrison duty, where it remained until 1863. While on the Vicksburg campaign, it served in W. S. Smith's Division, Sixteenth Corps. It was engaged in the Siege of Jackson; also, in the action on July 16th, in which Major Wm. J. Stephenson was mortally wounded. Having been transferred to the Fifteenth Corps, it marched to the relief of Chattanooga, where it took part in the battle of Missionary Ridge. It then marched on the winter campaign in East Tennessee for the relief of Knoxville, a campaign memorable for its hardships, privation, and suffering. The Forty-eighth fought in the Fifteenth Corps during the Atlanta campaign, being hotly engaged in the battle of July 22, 1864, in which Colonel Greathouse was killed. The regiment reënlisted, and hence it continued with the corps on its March through Georgia, and in the fighting in the Carolinas. It was then in Oliver's (3d) Brigade, Hazen's (2d) Division, Fifteenth Corps. After participating in the Grand Review in Washington at the close of the war, the regiment was ordered to Little Rock, Ark., where it was mustered out August 15, 1865.