Northfield is a village in Cook County, Illinois, United States, located approximately north of downtown Chicago. It is part of a collection of upscale residential communities north of Chicago that belong to New Trier Township and the greater North Shore. Its ZIP code, which it shares with neighboring Winnetka, is the 14th wealthiest in the nation according to Business Week. As of the 2010 census, the village's population was 5,420.