735 ILCS 5/13-122
No use of any land by any person or by the public generally, no matter how long continued, shall ever ripen into an easement by prescription, or be deemed to be an implied dedication, or be deemed to give rise to any other right, customary or otherwise, to be on, or to engage in activities on, such land, if the owner of such property for a continuous period posts at each entrance to the property or at intervals of not more than 200 feet along the boundary a sign reading substantially as follows: "Right of access by permission, and subject to control of owner".
If the entrances or boundaries of the property sought to be protected are paved, the sign referred to in this Section may be embedded in the pavement, provided that the inscription is legible and in letters at least as large as 24 point type.
The procedure provided in this Section does not constitute the exclusive method of preventing the use of land from creating an easement by prescription, an implied dedication or any other right to be on or to engage in activities on the land, but is in addition to any other methods now or hereafter provided by law. This Section shall not be applied retroactively to events which took place before October 1, 1975.
735 ILCS 5/13-122