Naperville ( NAY-pər-vil) 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 (45 km) 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. In 1839, after DuPage County was split from Cook County, Naperville became the county seat, which it remained until 1868. Beginning in the 1960s, Naperville experienced a significant population increase as a result of Chicago's urban sprawl. Naperville is home to Moser Tower and Millennium Carillon, one of the world's four largest carillons. It is also home to an extensive parks and forest preserve network, including Centennial Beach. The city has two school districts, 203 and 204. Naperville's largest employer is Edward Hospital with 4,500 employees. Naperville has a train station served by Amtrak and Metra.