331 Area Code
The 331 area code is serving portions of Chicago's near and far western suburbs, including the majority of DuPage County, Illinois.
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The 331 area code is serving portions of Chicago's near and far western suburbs, including the majority of DuPage County, Illinois.
Federal Data
State Data
County Data
City Data
Area code 331 covers a significant portion of the western suburbs of Chicago, Illinois. This includes areas within DuPage, Cook, Kane, and Will counties, as well as a small portion of Kendall County.
Area code 331 is an overlay to area code 630. Area code 630 was created in 1996. Area code 331 was introduced on October 7, 2007, overlaying area code 630. Ten-digit dialing is mandatory in this area.
Area code 331 is a general purpose code which was placed in service on October 7, 2007.
Our Illinois phone number lookup service will analyze the three-digit prefix of any 331 area code phone number and will show which telecommunications company and rate center it was initially assigned to. This prefix code data may help to determine the U.S. carrier, Illinois geographic region, and local calling area associated with the phone number.
Phone numbers follow the following structure under the North American Numbering Plan:
Understanding the area code can help you determine if a call is local to your area. However, keep in mind that due to mobile number portability and VoIP services, the caller may be anywhere in the United States, so it’s best to search for the most recent phone number details.
| Company | Number of Prefixes |
|---|---|
| CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL | 12 |
| NEW CINGULAR WIRELESS PCS, LLC - IL | 8 |
| T-MOBILE USA, INC. | 8 |
| SPRINT SPECTRUM, L.P. | 4 |
| BANDWIDTH.COM CLEC, LLC - IL | 3 |
| LEVEL 3 COMMUNICATIONS, LLC - IL | 2 |
| ILLINOIS BELL TEL CO | 1 |
| LOCAL ACCESS LLC - IL | 1 |
| MCIMETRO ACCESS TRANSMISSION SERVICES LLC - IL | 1 |
| ONVOY, LLC | 1 |
| OVATION COMMUNICATIONS OF ILLINOIS, INC. | 1 |
| PEERLESS NETWORK OF ILLINOIS, LLC - IL | 1 |
| RCN TELECOM SERVICES OF ILLINIOS, INC. - IL | 1 |
Carrier names have been updated from their original FCC assignments to reflect current companies following mergers, acquisitions, and rebranding. Updates were determined using AI-assisted research and may not be accurate or reflect up to date changes. This data is provided without warranties of accuracy or completeness.
| Rate Center | Number of Prefixes |
|---|---|
| NAPERVILLE | 12 |
| AURORA | 10 |
| ST CHARLES | 5 |
| DOWNERSGRV | 4 |
| ELMHURST | 3 |
| LEMONT | 3 |
| BARTLETT | 2 |
| BIG ROCK | 1 |
| SUGARGROVE | 1 |
| W CHICAGO | 1 |
| WHEATON | 1 |
| YORKVILLE | 1 |
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