65 ILCS 5/7-7-3
Any 2 or more municipalities, located in one or more counties each with less than 200,000 inhabitants according to the most recent federal census, which are contiguous or which upon consolidation shall be contiguous, may consolidate by compliance with this Division. Any 2 or more municipalities shall be deemed contiguous for purposes of this Division notwithstanding that they are separated by a park district or a forest preserve district, or by a railroad or public utility right-of-way or a highway or a toll highway under the jurisdiction of any township or any department or division of the State of Illinois, but upon consolidation, such park district, forest preserve district, right-of-way, highway or toll highway shall not be considered to be part of the consolidated municipality.
65 ILCS 5/7-7-3