Train stations are in many of the Chicago suburbs already and take on average 280,000[1] commuters to and from downtown Chicago on a daily basis (it's called the Metra system).
Hell, I just found out those same commuter lines extend all the way north to Kenosha, Wisconsin, and east to South Bend, Indiana, so into neighboring states. I did know people who commuted to Chicago from Indiana everyday so that's not too surprising.