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331 Area Code

Area code 331 serves Aurora, Naperville, Schaumburg, Bolingbrook, Wheaton and nearby communities in Illinois. It has been in service since October 7, 2007, when it was split from 630.

StateIllinois
Time zoneCentral
Local time now…
Prefixes in use224
Overlay with630
Projected to run out2080
AuroraNapervilleSchaumburgBolingbrookWheatonDowners GroveElmhurstLombardBartlettOswegoCarol StreamStreamwoodHanover ParkAddisonWoodridgeSt. CharlesGlendale HeightsGlen EllynYorkvilleBataviaWest ChicagoWestmontLisleRoselleBloomingdaleDarienMontgomeryVilla ParkGenevaNorth AuroraLemontHinsdaleWarrenvillePlanoCampton HillsWinfieldItascaSugar GroveBoulder HillWillowbrookClarendon HillsOak BrookElburnBerkeleyAuroraSchaumburgWheatonBartlettOswego
Cities and towns served by area code 331

Who issues 331 numbers

Mobile 45%VoIP and cable 38%Landline 17%

Share of the 224 prefixes (the three digits after 331) assigned to each type of carrier. Classification by carrier name, approximate.

CarrierPrefixes
Onvoy (Sinch)44
T-Mobile42
Verizon Wireless33
AT&T Mobility26
Fractel18
Bandwidth11
Ton80 Communications9
Lumen (Level 3)6

Cities and towns in area code 331

CityPopulationOther area codes
Aurora181,505630
Naperville153,114630
Schaumburg77,249847, 630, 708, 224
Bolingbrook74,803630
Wheaton54,065630
Downers Grove50,365630
Elmhurst46,111630
Lombard44,399630
Bartlett40,855630, 224
Oswego39,948630
Carol Stream39,315630, 224
Streamwood38,277630, 224
Hanover Park36,568630, 224
Addison35,758630
Woodridge34,028630
St. Charles33,594630
Glendale Heights32,655630
Glen Ellyn28,750630
Yorkville26,730630
Batavia26,586630
West Chicago25,296630
Westmont24,155630, 708, 847
Lisle23,432630
Roselle22,756847, 630, 708, 224
Bloomingdale22,476847, 630, 708, 224
Darien22,032630
Montgomery21,978630
Villa Park21,888630
Geneva21,138630
North Aurora19,406630
Lemont18,513630
Hinsdale17,573630, 708, 847
Warrenville15,211630
Plano12,677630
Campton Hills10,894630
Winfield10,146630
Itasca9,488630
Sugar Grove9,381630
Boulder Hill9,127630
Willowbrook9,126630, 708, 847

Showing the 40 largest of 44 places with 5,000+ residents.

Got a call from 331?

A 331 number was originally issued in Illinois, but that does not prove the caller is there. 38% of 331 prefixes belong to VoIP and cable providers, whose numbers can be bought online and used from anywhere. Caller ID can also be spoofed, so treat urgent requests for money, codes or passwords from any area code with suspicion, and call back on a number you already know.

All 224 prefixes in area code 331

Format: (331) XXX-YYYY. Carrier is the company the block was originally assigned to; numbers may since have been ported to another carrier.

Questions about area code 331

Where is area code 331?
Area code 331 is in Illinois. It covers Aurora, Naperville, Schaumburg, Bolingbrook, Wheaton, Downers Grove and 38 more cities and towns.
What time zone is area code 331?
Area code 331 is in the Central time zone.
Is 331 a toll-free number?
No. 331 is a geographic area code in Illinois. Toll-free numbers in the US start with 800, 833, 844, 855, 866, 877 or 888.
Why does 331 share its area with 630?
331 and 630 form an overlay: they cover the same territory, so new numbers there can get any of these codes, and local calls need all 10 digits.
Will area code 331 run out of numbers?
NANPA's latest forecast projects the 331/630 overlay to exhaust in the first quarter of 2080. Before that happens, a new area code is usually added as an overlay; existing numbers keep their code.

Other area codes in Illinois