Naperville is a city in DuPage and Will counties in the U.S. state of Illinois. It is a southwestern suburb of Chicago located 28 miles west of the city on the DuPage River. As of the 2020 census, its population was 149,540, making it the state's fourth-most populous city. Naperville was founded in 1831 by Joseph Naper. The city was established by the banks of the DuPage River and was originally known as Naper's Settlement. By 1832, over 100 residents lived in Naper's Settlement.