820 ILCS 165/1

For the purposes of this Act, the term "person" shall include any person, firm, partnership, association, corporation, or group of persons.

As used in this Act the term "employer" shall include any person, firm, partnership, association, corporation or group of persons employing a member or members of an association or union of workers having a collective bargaining contract or agreement with such person, firm, partnership, association, corporation or group of persons which contract or agreement requires payment of a stipulated minimum rate of wages.