70 ILCS 1310/2
Any such elevated pleasure highway or boulevard may be constructed upon, along or over any public park, parkway, pleasureway, driveway, boulevard, street or alley now or hereafter under the control of the board of park commissioners, or, when, in the judgment of the board of park commissioners, the public good will be served thereby, a part or parts of the elevated highway or boulevard may be constructed upon land not now used for public purposes. In the event that the board of park commissioners desire to construct an elevated pleasure highway or boulevard in whole or in part upon a street, road or alley not under its jurisdiction, it may proceed to do so by obtaining the consent of the political subdivision having jurisdiction thereof, and the consent in writing of the owners of a majority of the lineal front feet of the property abutting on such street, road or alley proposed to be taken over by the park district, provided, however, in streets, roadways or boulevards having a width greater than 66 feet between lot lines, no such frontage consents shall be necessary, where the outside line of the proposed elevated pleasure highway or boulevard structure, substructure or superstructure shall be more than 25 feet from the abutting property line.
70 ILCS 1310/2