55 ILCS 125/5

The county board of each county which has not heretofore procured a copy of the original field notes and plats of the United States surveys of the lands in such county, shall procure such copies from the custodian of the originals of such field notes and plats at the cost of the county. The copies of such field notes and plats which have been or shall be procured hereafter by any county shall be deposited and kept in the office of the recorder of the county, and be at all reasonable times subject to examination by all persons who may desire to examine same. All surveys shall be made in accordance with the original surveys and the laws of the United States governing surveys.