Chicago is the freight rail capital of the US; it's the national hub. It's also the hub for a number of interstate highways. Distribution firms want to be near both modes of transportation, and the greater Chicago metroplex offers that in spite of predatory taxes and a confiscatory labor union system.
Once the CREATE project untangles and unjams the bowels of Chicago's freight yards and facilitates movement through the area, it will become even more desirable as a location for distribution.
The state of Illinois is controlled by unions and all of the new warehouse distribution laborers will be unionized, and if not, those businesses will be pressured to either shut down or unionize.
Illinois is not a right to work state. 