On 19 October 1920, units of the Oklahoma National Guard were organized as part the 45th Infantry Division, also manned with troops from Arizona, Colorado, and New Mexico. The division was formed and federally recognized as a National Guard unit on 3 August 1923 in Oklahoma City, Oklahoma. It was assigned the 89th Infantry Brigade of the Colorado and Arizona National Guards, and the 90th Infantry Brigade of the Oklahoma National Guard. As a consequence of these militia roots, when the division was properly organized, many of its members were marksmen and outdoorsmen from the remote frontier regions of the Southwestern United States. The division's first commander was Major General Baird H. Markham.