70 ILCS 1205/3-1
Any territory adjoining a park district, or separated therefrom only by a river, stream or other body of water, street, alley, roadway, highway, toll road, or railroad, may become a part of the district if a majority of the legal voters residing in and a majority of the property owners of record within the territory proposed to be annexed to the district petition the board of the district to be annexed. The board may, in its discretion, by ordinance, annex the territory to the district, and the territory shall then become and be a part of the district the same as though originally included in the district. No tract of land, however, exceeding 20 acres in area shall be included in an annexation petition without the written consent of the owner of record unless the tract is (1) subdivided into lots or blocks or (2) bounded on at least 3 sides by lands subdivided into lots or blocks. A certified copy of the annexing ordinance shall be filed in the offices of the county clerk and Recorder of each county in which the annexation takes place. The new boundary shall extend to the far side of any adjacent highway and shall include all of every highway within the area annexed. These highways shall be considered to be annexed even though not included in the legal description set forth in the annexation ordinance.
70 ILCS 1205/3-1