The 189th Field Artillery Regiment, today consists of 1st Battalion, 189th Field Artillery Regiment, and 2nd Battalion (General Services) Field Artillery Regiment which are headquartered in Oklahoma City, Oklahoma. It was a part of the 45th Infantry Division, Oklahoma Army National Guard. The Regiment only retains its affiliation with the Field Artillery branch for purposes of history and lineage and is the core cadre and leadership of the Oklahoma Regional Training Institute (OKRTI). Its parent unit is the 90th Troop Command, a successor unit to the 45th Division.