Where Is Area Code 331?
Area code 331 serves Aurora, Illinois, and nearby western and southwestern Chicago suburbs. It covers northeastern Illinois in the Great Lakes region and shares its geographic footprint with area code 630.
The 331 numbering area includes communities in DuPage, Kane, Kendall, Will, and western Cook counties. Major communities include Naperville, Wheaton, St. Charles, Geneva, Batavia, West Chicago, and Lisle.
The Fox River is a notable geographic feature in the region. It passes through Aurora, Batavia, Geneva, and St. Charles. The area also includes Fermilab in Batavia and the Morton Arboretum in Lisle.
Cities and Communities in the 331 Area Code
- Addison, DuPage County
- Aurora, DuPage, Kane, Kendall, and Will counties
- Batavia, Kane County
- Bensenville, DuPage County
- Bloomingdale, DuPage County
- Bolingbrook, DuPage and Will counties
- Carol Stream, DuPage County
- Clarendon Hills, DuPage County
- Darien, DuPage County
- Downers Grove, DuPage County
- Elmhurst, Cook and DuPage counties
- Geneva, Kane County
- Glen Ellyn, DuPage County
- Glendale Heights, DuPage County
- Hanover Park, DuPage County
- Hinsdale, Cook and DuPage counties
- Itasca, DuPage County
- Lisle, DuPage County
- Lombard, DuPage County
- Montgomery, Kane and Kendall counties
- Naperville, DuPage and Will counties
- North Aurora, Kane County
- Oak Brook, DuPage County
- Oakbrook Terrace, DuPage County
- Oswego, Kendall County
- Plainfield, Kendall and Will counties
- St. Charles, DuPage and Kane counties
- Sugar Grove, Kane County
- Villa Park, DuPage County
- Warrenville, DuPage County
- Wayne, DuPage County
- West Chicago, DuPage County
- Westmont, DuPage County
- Wheaton, DuPage County
- Willowbrook, DuPage County
- Winfield, DuPage County
- Wood Dale, DuPage County
- Woodridge, DuPage and Will counties
- Yorkville, Kendall County
History of Area Code 331
Area code 331 entered service on June 2, 2007, as an overlay for area code 630. An overlay adds a second area code to the same geographic region, so 331 did not replace 630 or change the communities in the existing service area.
Area code 630 was created in 1996 through a split of area code 708. The 1996 split and the 2007 overlay added numbering capacity for the growing western Chicago suburban telephone network.
Key Facts About Area Code 331
- Area code 331 is an Illinois area code, and Aurora is its primary city.
- Area code 331 is located in the U.S. Census Bureau’s Great Lakes region.
- Area code 331 uses Central Time.
- Area code 331 is a geographic area code, not a toll-free code.
- Area code 331 is an overlay of area code 630.
- Area code 331 entered service on June 2, 2007.
- Area code 331 reaches parts of Cook, DuPage, Kane, Kendall, and Will counties.
- Aurora University is located in Aurora, and Fermilab is located in Batavia within the 331 geographic area.
Frequently Asked Questions
What state is area code 331 in?
Area code 331 is in Illinois.
What major cities use area code 331?
Major cities and communities using area code 331 include Aurora, Naperville, Wheaton, and St. Charles.
What time zone is area code 331 in?
Area code 331 is in Central Time.
Is area code 331 a toll-free number?
No. Area code 331 is a geographic area code, not a toll-free number.