35 ILCS 200/10-440

The sale or transfer of unimproved land does not affect the valuation of the land, unless there is a change in the use of the land or the acreage requirement is no longer met. Any tract of land containing less than 5 acres after a sale or transfer may be reclassified by the chief county assessment officer and valued as otherwise permitted by law. The taxpayer and the Department of Natural Resources may revise a conservation management plan whenever there is a change in the ownership of the affected land.