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Area code 331

Area code 331 Aurora, Illinois

Area code 331 is in Illinois, with numbers assigned in Aurora, Naperville, Downers Grove and 21 more places. It’s 11:10 PM there now.

State
Illinois17 area codes in Illinois
Time zone
Central11:10 PM there now
Exchanges
22424 places
Overlay
630Same area, 10-digit dialing
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Where area code 331 is

Numbers in 331 are assigned to 24 places in 5 counties: DuPage County, Will County, Kane County, Kendall County and Cook County.

Aurora has the most, 20% of the exchanges; the rest are spread across 23 other places.

  • Aurora45
  • Naperville33
  • Downers Grove21
  • St. Charles18
  • Lombard13
  • Elmhurst10
  • Lemont10
  • Bartlett8
  • Wheaton8
  • West Chicago8
  • Oswego7
  • Geneva7
  • Sugar Grove6
  • Hinsdale6
  • Yorkville4
  • Itasca3
  • Elburn3
  • Glen Ellyn3
  • Warrenville2
  • Batavia2
  • Big Rock2
  • Plano2
  • Kaneville2
  • Roselle1

Phone companies in 331

224 blocks of numbers in 331 are held by 24 phone companies. The most belong to T-Mobile (43), Inteliquent (39) and Verizon Wireless (33).

A large share, about 50%, belongs to competitive and internet phone carriers; wireless networks hold 46% and local phone and cable companies 5%.

A block’s holder is the company it was first assigned to; numbers can move to other carriers since.

History and overlays

331 went into service in 2007, added to the area of 630.

630 (since 1996) shares the same area, so a new number there can get any of these codes and local calls are dialed with all 10 digits.

76 new exchanges were assigned since 2021, the latest in August 2026.

Calling 331

It’s 11:10 PM Central time in 331 right now.

From elsewhere in the U.S., dial 1, 331 and the 7-digit number; inside the area, all 10 digits too.

Nearby area codes

Illinois has 17 area codes: 217, 224, 309, 312, 331, 447, 464, 618, 630, 708, 730, 773, 779, 815, 847, 861 and 872.

From the North American Numbering Plan Administrator’s area code and exchange records (10/22/2026) and U.S. Census place and county names. Places and companies are where number blocks were assigned, not where anyone lives or which carrier a number uses today.

Map of the 331 area code

Map of the 331 area code around Aurora, Naperville and Downers Grove, Illinois.

Interactive map © OpenStreetMap contributors

Cities on the map

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Questions about 331

Where is area code 331?

In Illinois, covering Aurora, Naperville and Downers Grove and other places across 5 counties.

What time zone is 331 in?

Central time. It was 11:10 PM there when this page loaded.

Is 331 an overlay?

Yes. 630 serves the same area, so dial all 10 digits for local calls.

Which phone companies have 331 numbers?

24 companies hold blocks; the most belong to T-Mobile, Inteliquent and Verizon Wireless. About 46% of blocks are wireless.

Is 331 running out of numbers?

Not on record. 76 new exchanges have been assigned since 2021.