65 ILCS 5/7-1-8
Any territory which is not within the corporate limits of any municipality but which is contiguous to a municipality at the time of annexation and which territory has no electors residing therein, or any such territory with electors residing therein, may be annexed to the municipality in the following manner: a written petition signed by the owners of record of all land within such territory and by at least 51% of the electors residing therein shall be filed with the municipal clerk. The petition shall request annexation and shall state that no electors reside therein or that at least 51% of such electors residing therein join in the petition, whichever shall be the case, and shall be under oath. The corporate authorities of the municipality to which annexation is sought shall then consider the question of the annexation of the described territory. A majority vote of the corporate authorities then holding office is required to annex. The vote shall be by "yeas" and "nays" entered on the legislative records. A copy of the ordinance annexing the territory together with an accurate map of the annexed territory shall be recorded with the recorder and filed with the County Clerk within the county wherever the annexed territory is located.
65 ILCS 5/7-1-8