65 ILCS 5/11-13-14
The regulations imposed and the districts created under the authority of this Division 13 may be amended from time to time by ordinance after the ordinance establishing them has gone into effect, but no such amendments shall be made without a hearing before some commission or committee designated by the corporate authorities. Notice shall be given of the time and place of the hearing, not more than 30 nor less than 15 days before the hearing, by publishing a notice thereof at least once in one or more newspapers published in the municipality, or, if no newspaper is published therein, then in one or more newspapers with a general circulation within the municipality. In municipalities with less than 500 population in which no newspaper is published, publication may be made instead by posting a notice in 3 prominent places within the municipality. In case of a written protest against any proposed amendment of the regulations or districts, signed and acknowledged by the owners of 20% of the frontage proposed to be altered, or by the owners of 20% of the frontage immediately adjoining or across an alley therefrom, or by the owners of the 20% of the frontage directly opposite the frontage proposed to be altered, is filed with the clerk of the municipality, the amendment shall not be passed except by a favorable vote of two-thirds of the alderpersons or trustees of the municipality then holding office. In such cases, a copy of the written protest shall be served by the protestor or protestors on the applicant for the proposed amendments and a copy upon the applicant's attorney, if any, by certified mail at the address of such applicant and attorney shown in the application for the proposed amendment. Any notice required by this Section need not include a metes and bounds legal description, provided that the notice includes:
65 ILCS 5/11-13-14