The first 38th United States Colored Infantry Regiment served from January 23, 1864, to January 25, 1867.

The second 38th Infantry was first established on 28 July 1866, as part of the Regular Army, one of six segregated, all-black regiments created following the Civil War. It was organized on 1 October of that year at Jefferson Barracks, Missouri, and was stationed in New Mexico Territory and along the transcontinental railroads then under construction. Cathay Williams, the first recorded African American female to serve in the U.S. Army, served with the 38th during this time, disguised as a male. On 15 March 1869, the 38th was consolidated with the 41st Infantry Regiment and redesignated as the 24th Infantry Regiment.