Chicago is a town.
Chicago . With over 2.7 million residents , it is also the most populous city in both the state of Illinois and the Midwestern United States . Chicago was incorporated as a city in 1837 , near a portage between the Great Lakes and the Mississippi River watershed , and grew rapidly in the mid-nineteenth century . In 2012 , Chicago was listed as an alpha global city by the Globalization and World Cities Research Network , and ranked seventh in the world in the 2016 Global Cities Index . In 2016 , Chicago hosted over 54 million domestic and international visitors , a new record making it one of the top visited cities in the nation . The city has many nicknames , the best-known being the Windy City .