(765 ILCS 5/31) (from Ch. 30, par. 30)
    Sec. 31. Deeds, mortgages and other instruments of writing relating to real estate shall be deemed, from the time of being filed for record, notice to subsequent purchasers and creditors, though not acknowledged or proven according to law; but the same shall not be read as evidence, unless their execution be proved in manner required by the rules of evidence applicable to such writings, so as to supply the defects of such acknowledgment or proof.
(Source: Laws 1871-2, p. 282.)