Smith resigned his volunteer commission and was mustered out of the volunteers on January 15, 1866. He then became colonel of the U.S. 7th Cavalry Regiment, serving in the American West. He retired from the military service in April 1869 to become postmaster of St. Louis, Missouri, where he died on January 30, 1897. He was buried at Bellefontaine Cemetery in St. Louis.Eicher, 2001, p. 493.
