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zipcodes.pro — AREA-CODE/331

331 area code

Area code 331 is in Illinois. It covers Aurora, Naperville, Schaumburg and 45 other places: 78 ZIP codes in DuPage, Kane, Kendall and 2 other counties. Local time there is , Central Time. In service since 2007 as an overlay: it covers the same area as 630, so a number from there can have either code.

Time zone
Central
Largest city
Aurora
Overlays
630
In service since
2007
Rate centres
24
Prefixes assigned
224 (2,240,000 numbers)

Who calls from a 331 number

NANPA records the carrier each block of 331 numbers is assigned to. Of the 2.1 million 331 numbers assigned, 58% are with cable, internet-calling, business and other carriers (Onvoy, Bandwidth and Peerless Network Of Illinois); 41% with mobile carriers (T-Mobile, AT&T Mobility and Verizon Wireless); 2% with local phone companies.

That is who the numbers were assigned to: people keep their number when they change carrier, so any one number may have moved since.

Carriers holding the most 331 numbers
CarrierKindShare
OnvoyCable, VoIP, other27%
T-MobileMobile14%
AT&T MobilityMobile14%
Verizon WirelessMobile13%
BandwidthCable, VoIP, other8%
Peerless Network Of IllinoisCable, VoIP, other3%

An area code says where a number was issued, not where the caller is: people keep their numbers when they move, and caller ID can be set to show any number, which the FCC calls spoofing. If a call you did not expect asks for money or personal details, the FCC advises hanging up and calling the company back on a number you look up yourself. Unwanted calls can be reported to the FTC at ReportFraud.ftc.gov.

Places in area code 331

The 24 places with a telephone rate centre of their own using 331, largest first. Each links to its ZIP codes.

Places in area code 331
PlaceZIP codesPopulation
Aurora, IL 10 179,898
Naperville, IL 6 150,692
Wheaton, IL 2 53,557
Downers Grove, IL 2 50,054
Elmhurst, IL 1 45,671
Lombard, IL 1 43,619
Bartlett, IL 1 40,501
Oswego, IL 1 36,375
St. Charles, IL 2 32,854
Glen Ellyn, IL 2 28,390
Batavia, IL 1 27,151
West Chicago, IL 2 25,395
Yorkville, IL 1 23,617
Roselle, IL 1 22,752
Geneva, IL 1 21,258
Lemont, IL 1 17,820
Hinsdale, IL 2 17,175
Warrenville, IL 1 14,718
Plano, IL 1 12,203
Itasca, IL 1 9,355
Sugar Grove, IL 1 9,240
Elburn, IL 1 6,354
Big Rock, IL 1 1,548
Kaneville, IL 1 523

Nearby places using 331

These places have no rate centre of their own in NANPA's records; the nearest one uses 331. Near an area-code boundary that can be wrong for part of a town.

ZIP codes in area code 331

78 ZIP codes in 46 towns, by the town each is mailed to, largest first. Each links to its own page.

Where 331 numbers are issued

NANPA's rate centres with the most 331 prefixes (each prefix is 10,000 numbers), under NANPA's own abbreviated names.

Rate centres using area code 331
Rate centrePlacePrefixes
AURORA Aurora 45
NAPERVILLE Naperville 33
DOWNERSGRV Downers Grove 21
ST CHARLES Saint Charles 18
LOMBARD Lombard 13
ELMHURST Elmhurst 10

Counties

The counties of its ZIP codes, most residents first, with how many of its ZIP codes each has.

Which code covers where you are now? What area code am I in? answers from your location.

Questions about area code 331

Where is area code 331?

Area code 331 is in Illinois. It covers Aurora, Naperville, Schaumburg and 45 other places: 78 ZIP codes in DuPage, Kane, Kendall and 2 other counties.

What ZIP codes are in area code 331?

78 ZIP codes, by the town each is mailed to: Aurora (10, 60502 to 60598), Naperville (6, 60540 to 60567), Schaumburg (7, 60159 to 60196), Wheaton (2, 60187 to 60189) and 42 more towns. The full list is on this page.

What time zone is area code 331 in?

Central time.

Is a 331 number a mobile or a landline?

It can be either. 41% of 331 numbers are assigned to mobile carriers and 2% to local phone companies (NANPA, 2026-10-10); the rest are with cable, internet-calling, business and paging carriers. A number keeps its area code when it moves to another carrier.

What area codes overlay 331?

630. They cover the same area as 331, so a new number there can be given any of them.

Does a 331 number mean the caller is in Illinois?

Not necessarily. An area code says where the number was first issued. People keep their numbers when they move or switch carriers, and calling software can show any number, so a 331 call can come from anywhere.

Other area codes in Illinois

All 17 Illinois area codes, by area, with the cities each covers

Source: NANPA NPA database, central office code and thousands-block assignments, 2026-10-10. Places are matched to NANPA's rate centres by name; see sources.

Cite this page

zipcodes.pro. “Area code 331.” Data release 2026-10-12. Retrieved 2026-10-20. https://zipcodes.pro/area-code/331

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