65 ILCS 5/7-1-12
Upon a written petition which is signed by a majority of the owners of record of land in any contiguous unincorporated territory wholly bounded by 2 or more municipalities and after the notice required by this Section has been given, the specified territory may be annexed by any one of the specified municipalities by the passage of an ordinance providing therefor. The corporate authorities of the annexing municipality shall cause notice of the filing of such petition to be published once, in a newspaper of general circulation within the territory to be annexed, not less than 10 days before the passage of the annexation ordinance. When the territory to be annexed lies wholly or partially within a township other than that township where the municipality is situated, the annexing municipality shall give at least 10 days prior written notice of the time and place of the passage of the annexation ordinance to the township supervisor of the township where the territory to be annexed lies. The ordinance shall describe the territory annexed, which may not exceed 1/3 the area of the annexing municipality before the annexation. A copy of the annexing ordinance and an accurate map of the annexed territory shall be recorded by the recorder of the county wherein the annexed territory is situated and a document of annexation shall be filed with the county clerk and County Election Authority.
65 ILCS 5/7-1-12