820 ILCS 235/2
The term "employer" as used in this Act shall mean and include an individual, a partnership, an association, a corporation, a legal representative, trustee, receiver, trustee in bankruptcy, and any common carrier by rail, motor, water, air or express company doing business in or operating within the State.
(from Ch. 48, par. 172e)
(Source: Laws 1951, p. 1308.)