70 ILCS 1205/3-8
Upon a written petition, signed by a majority of the owners of record of land in any contiguous territory not incorporated within a park district, wholly bounded by 2 or more park districts, the specified territory may be annexed by any one of the specified park districts by the passage of an ordinance providing therefor. The ordinance shall describe the territory annexed, which shall not exceed one-third of the area of the annexing park district before the annexation. The park district to which the territory is to be annexed shall send a copy of the proposed annexing ordinance, by certified mail, at least 30 days before the annexing ordinance takes effect, to the last known addresses, if any, ascertained upon diligent search, of the owners of record of land in that territory. A certified copy of the annexing ordinance and an accurate map of the annexed territory shall be filed in the offices of the county clerk and recorder of each county in which annexation takes place.
70 ILCS 1205/3-8