Chicago is a city in Illinois, one of the major cities in the United States of America. It is the hometown of former NYPD Detective Joe Fontana.
Chicago was also the home of Kathleen Shaw, who ran away to New York City to escape her abusive husband Julian Shaw. (CI: "Renewal")
It is the main setting of Chicago Fire and its spin-offs Chicago P.D., Chicago Med, and Chicago Justice, the franchise of which is connected with the Law & Order franchise.