The Twelfth Texas Infantry was organized and mustered into service at Waco, Texas, in the spring of 1862. It is often mistakenly referred to as the Eighth Texas Infantry. It comprised ten companies, lettered A to K, with men from several Texas counties including Bosque, Brazos, Comanche, Freestone, Grimes, Hill, Lavaca, McLennan, Milam, Red River, and Rusk. The regimental commander was Col. Overton Young. Other field officers were Lt. Col. William Clark, Lt. Col. James W. Raine, and Maj. Erastus W. Smith. The regiment was assigned to Waul's Texas Legion and served in Walker's Texas Division.
By October 1862 the regiment was transferred to the LaFourche District of Louisiana. From this point to war's end the regiment saw an extensive amount of combat in Louisiana and Arkansas. The regiment took part in the following battles during the Red River campaign—Mansfield on April 8, 1864, Pleasant Hill on April 9, 1864, and Jenkins' Ferry on April 30, 1864. The regiment spent the summer of 1864 in Central Arkansas and was eventually ordered to Marshall, Texas, in the early spring of 1865. The regiment then marched to Hempstead, Texas, where it was among the forces surrendered by Gen. E. Kirby Smith on May 23, 1865.