Chicago is a city.
Chicago ( [ ʃᵻˈkɑːɡoʊ ] or [ ʃᵻˈkɔːɡoʊ ] ) , officially the City of Chicago , is the third-most populous city in the 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 . The city has many nicknames , the best-known being the Windy City .