65 ILCS 5/7-3-4
Any territory, within any municipality, which is upon the border but within the boundary of the municipality may be disconnected from the municipality, in the discretion of its corporate authorities as follows:
A written petition, signed by owners of record representing a majority of the area of land in such territory, shall be filed with the clerk of the municipality, requesting that the specified territory be disconnected from the municipality. The petition shall be filed at least 30 days before it is considered by the corporate authorities. The petition shall be accompanied with the certificate of the proper county clerk, showing that all city taxes or assessments due up to the time of presenting the petition are fully paid. The corporate authorities, in their discretion, may disconnect the territory from the municipality, by an ordinance passed by a majority of the members elected to the city council, or board of trustees, as the case may be.
65 ILCS 5/7-3-4