765 ILCS 215/1

Whenever the owner or owners of adjacent tracts of land shall desire to establish permanently the lines and corners thereof between them, he, she or they may enter into a written agreement to employ and abide by the survey of some surveyor, and after said survey is completed, a plat thereof with a description of all corners and lines plainly marked thereon, together with the written agreement of the parties, shall be recorded in the recorder's office of the county where the lands are situated; and the lines and corners of said survey so made and recorded, shall be binding upon the parties entering into said agreement, their heirs, successors and assigns, and shall never be changed.