Some cities covered by area code 331 are Addison, Bartlett, Batavia, Bensenville, Bloomingdale, Bolingbrook, Carol Stream, Darien, Downers Grove, Elmhurst, Glen Ellyn, Glendale Heights, Hanover Park, Lisle, Lombard, Naperville, North Aurora, Roselle, Saint Charles, Streamwood, Villa Park, West Chicago, Westmont, Wheaton, Woodridge