65 ILCS 5/7-5-1
Whenever a municipality incorporated under any general or special law is in danger of losing all or the greater portion of the land within its corporate limits by reason of the washing away of the bank of any river, or whenever the inhabitants of any limited territory who, as inhabitants of that territory, have land within this State held as a common by virtue of a grant by any person or government having power to make that grant, are in danger of losing all or the greater portion of the territory by reason of the washing away of the bank of any river, that municipality or those inhabitants may acquire by gift or purchase suitable real estate to which the site of that municipality, or of the residence of those inhabitants may be removed. However, this real estate shall be within 3 miles of the former nearest limit of that municipality or territory and shall not be more than is reasonably necessary for the purposes of a new site.
65 ILCS 5/7-5-1