The Military Department traces its history to 1890 when the United States Congress authorized one regiment of organized militia for Oklahoma Territory.

Following that authorization, the Territorial Legislature passed a law in 1895 which provided for the organization and development of the Volunteer Militia, which later became the Oklahoma National Guard.

The Joint Staff assists the Adjutant General in the decision making and execution process of the Military Department.

The sole function of the Joint Staff is command support, and its only authority is that which is delegated to it by the Adjutant General.

The Joint Staff assists the Adjutant General in accomplishing his responsibilities for strategic direction of the Department, ensuring operation of all units under unified command, and their integration into land and air forces.