Mo. Rev. Stat. § 41.150
The adjutant general may assign two assistant adjutants general in the grade of brigadier general or below, one from the ground forces and the other from the air forces of this state, as well as a third assistant adjutant general in the grade of major general or below from the air forces of this state, who, at the time of their appointment, have not less than four years of previous military service as a commissioned officer with the military forces of this state, another state or territory, the District of Columbia or the United States, or in any or all such services combined. The assistant adjutants general shall perform such duties as are assigned by the adjutant general; and during the absence of the adjutant general from the state, and during any period when the adjutant general is unable to perform such duties, the senior assistant adjutant general may perform the duties of the adjutant general. The assistant adjutants general shall serve in the grade and receive such compensation as the adjutant general determines.
(L. 1951 p. 654 § 24, A.L. 1953 p. 561, A.L. 1961 p. 479, A.L. 2002 H.B. 2047)