Area code 331 is an overlay for area code 630 and serves parts of Chicago’s western suburbs, including cities like Aurora, Naperville, and Wheaton. Introduced in 2007, this area is part of the greater Chicagoland region. Naperville, one of the largest cities in this zone, is known for its excellent schools, Riverwalk park along the DuPage River, and a thriving downtown full of shops and restaurants. It offers suburban comfort with easy access to the city.