65 ILCS 5/11-102-1

Every municipality with a population of 500,000 or more may establish and maintain public airports, upon (1) any land either within or outside the corporate limits of the municipality, (2) any public waters of the State of Illinois within the limits or jurisdiction of or bordering on the municipality, (3) any submerged land under such public waters, and (4) any artificial or reclaimed land which before the artificial making or reclamation thereof constituted a portion of the submerged land under such public waters.