Area Code 331 History:
Area code 331 was put into service. Area code 331 is an overlay of area code 630.
Counties in Illinois within area code 331 include:
DuPage County, Kane County, Cook County, Will County, and Kendall County.
Major cities or places in Illinois within area code 331 include:
Area codes 331 and 630 serve many of the western suburbs of Chicago including the cities and communities of Aurora, Bartlett, Batavia, Bensenville, Bloomingdale, Bolingbrook, Carol Stream, Darien, Downers Grove, Elmhurst, Glen Ellyn, Glendale Heights, Hanover Park, Lisle, Lombard, Naperville, Roselle, St. Charles, Streamwood, Villa Park, West Chicago, Westmont, Wheaton and Woodridge in addition to many smaller communities within the area codes 331 and 630 service area.