3rd Infantry Regiment was assembled during the spring of 1861 with men from Iberville, Morehouse, Winn, De Soto, Caddo, and Caldwell parishes. The unit fought at Wilson's Creek and Elkhorn Tavern, then moved to Mississippi where it was active in the conflicts at Iuka and Corinth. Later it was assigned to L. Hebert's Brigade in the Department of Mississippi and East Louisiana and was captured in the fight at Vicksburg. After being exchanged, the regiment served in A. Thomas' Brigade, Trans-Mississippi Department. It contained 271 officers and men in March, 1862, lost forty percent of the 264 at Iuka, and totalled 38 effectives in December, 1863. Early in 1865 the 3rd disbanded. The field officers were Colonels Frank C. Armstrong, Jerome B. Gilmore, Louis Hebert, and Samuel D. Russell; Lieutenant Colonels O.P. Amacker, Samuel M. Hyams, and David Pierson; and Majors John S. Richards and William F. Tunnard.