5 ILCS 275/2
Because of the existing possibility of attack upon the United States of unprecedented size and destructiveness, and in order, in the event of such an attack, to assure continuity of government through legally constituted leadership, authority and responsibility in the offices of the government of the state and its political subdivisions; to provide for the effective operation of governments during an emergency; to assure the continuity of local governments in the event of other natural or manmade disasters; and to facilitate the early resumption of functions temporarily suspended, it is found and declared to be necessary to provide for additional officers who can exercise the powers and discharge the duties of governor; to provide for emergency interim succession to governmental offices of this State and its political subdivisions in the event the incumbents thereof (and their deputies, assistants or other subordinate officers authorized, pursuant to law, to exercise all of the powers and discharge the duties of such offices, hereinafter referred to as deputies) are unavailable to perform the duties and functions of such offices.
5 ILCS 275/2