Area code 331 prefixes
224 of the 786 possible NXX blocks are assigned in area code 331 (28.5% of capacity), spread across 24 rate centers and 25 holders. The largest holders are T-MOBILE USA, INC. (42 blocks, 18.8%), ONVOY, LLC (39 blocks, 17.4%), CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL (33 blocks, 14.7%). Grouped by brand, T-Mobile accounts for 43 blocks; brand-attributable holders cover 85% of the code, and the rest are CLECs, VoIP wholesalers and regional carriers that trade under their own names. The assignment records here run from 2007-07-06 to 2026-08-14, with 21 blocks handed out in 2021 alone. 223 blocks (100%) are in thousands-block pooling, meaning the block is shared between carriers in 1,000-number lots rather than held whole – which is why a single NXX can serve several carriers at once. 2 assigned blocks (347, 349) are not yet in service: assigned to a carrier but not open for calls, so a caller ID from one is spoofed. 172 were growth assignments – additional blocks to a carrier that had already filled its earlier ones.
Largest holders in 331
| Holder of record, as NANPA names it | Brand | Blocks | Share |
|---|---|---|---|
| T-MOBILE USA, INC. | T-Mobile | 42 | 18.8% |
| ONVOY, LLC | Onvoy | 39 | 17.4% |
| CELLCO PARTNERSHIP DBA VERIZON WIRELESS - IL | Verizon | 33 | 14.7% |
| NEW CINGULAR WIRELESS PCS, LLC - IL | AT&T | 26 | 11.6% |
| FRACTEL, LLC | – | 18 | 8% |
| BANDWIDTH.COM CLEC, LLC - IL | Bandwidth | 11 | 4.9% |
| TON80 COMMUNICATIONS, LLC | – | 9 | 4% |
| LEVEL 3 COMMUNICATIONS, LLC - IL | Lumen | 6 | 2.7% |
| PEERLESS NETWORK OF ILLINOIS, LLC - IL | Peerless | 5 | 2.2% |
| ONVOY SPECTRUM, LLC | Charter | 5 | 2.2% |
| MCIMETRO ACCESS TRANSMISSION SERVICES LLC - IL | Verizon | 4 | 1.8% |
| TELEPORT COMMUNICATIONS AMERICA, LLC - IL | AT&T | 4 | 1.8% |
Names are printed as they appear in the assignment records, which is the legal entity rather than the brand. Holding a block is not the same as serving the numbers in it: portability moves numbers between carriers and pooling splits a block between several.
Rate centers with their own page
Rate centers where at least three blocks are assigned, excluding the numbered metro zone codes. The remainder are in the full table below.
All 224 assigned blocks
One row per NXX. “Pooled” means carriers draw 1,000-number lots from the block rather than holding all 10,000, so a pooled prefix can belong to several carriers at once. “Not in service” means assigned but not yet open for calls – a caller ID from one of those is necessarily spoofed. The holder column gives the brand where the legal entity maps to one; the full legal names are in the holders table above, exactly as NANPA records them.
| Prefix | Holder of record | Rate center | Assigned | Pooled | In service |
|---|---|---|---|---|---|
| 331-200 | T-Mobile | BARTLETT | 2011-07-11 | yes | yes |
| 331-201 | Verizon | DOWNERSGRV | 2012-01-06 | yes | yes |
| 331-202 | T-Mobile | ELMHURST | 2012-01-17 | yes | yes |
| 331-203 | T-Mobile | AURORA | 2011-10-12 | yes | yes |
| 331-204 | Onvoy | NAPERVILLE | 2015-12-10 | yes | yes |
| 331-205 | T-Mobile | AURORA | 2011-10-21 | yes | yes |
| 331-206 | T-Mobile | AURORA | 2011-10-12 | yes | yes |
| 331-207 | Lumen | YORKVILLE | 2011-11-01 | yes | yes |
| 331-208 | Lumen | AURORA | 2011-11-08 | yes | yes |
| 331-209 | Lumen | ELMHURST | 2012-01-17 | yes | yes |
| 331-210 | Peerless | ST CHARLES | 2012-03-06 | yes | yes |
| 331-212 | Verizon | AURORA | 2012-04-05 | yes | yes |
| 331-213 | Verizon | NAPERVILLE | 2011-09-06 | yes | yes |
| 331-214 | Verizon | DOWNERSGRV | 2012-06-20 | yes | yes |
| 331-215 | Verizon | NAPERVILLE | 2012-09-28 | yes | yes |
| 331-216 | AT&T | OSWEGO | 2012-10-31 | yes | yes |
| 331-217 | Onvoy | LOMBARD | 2023-07-11 | yes | yes |
| 331-218 | T-Mobile | WHEATON | 2013-07-09 | yes | yes |
| 331-219 | Telnyx | AURORA | 2017-03-16 | yes | yes |
| 331-220 | T-Mobile | AURORA | 2011-07-12 | yes | yes |
| 331-221 | AT&T | ELMHURST | 2009-01-21 | yes | yes |
| 331-222 | AT&T | ST CHARLES | 2008-10-28 | yes | yes |
| 331-223 | AT&T | ST CHARLES | 2008-10-28 | yes | yes |
| 331-224 | Onvoy | ITASCA | 2023-06-05 | yes | yes |
| 331-225 | T-Mobile | ELMHURST | 2011-08-22 | yes | yes |
| 331-226 | T-Mobile | NAPERVILLE | 2017-03-20 | yes | yes |
| 331-227 | Verizon | SUGARGROVE | 2016-05-17 | yes | yes |
| 331-228 | Windstream | ST CHARLES | 2011-09-21 | yes | yes |
| 331-229 | Verizon | NAPERVILLE | 2012-11-27 | yes | yes |
| 331-230 | T-Mobile | AURORA | 2017-04-05 | yes | yes |
| 331-231 | AT&T | NAPERVILLE | 2017-08-07 | yes | yes |
| 331-232 | AT&T | W CHICAGO | 2017-08-08 | yes | yes |
| 331-233 | Telnyx | DOWNERSGRV | 2017-03-13 | yes | yes |
| 331-234 | Verizon | SUGARGROVE | 2013-07-08 | yes | yes |
| 331-235 | AT&T | ST CHARLES | 2017-10-17 | yes | yes |
| 331-236 | T-Mobile | WHEATON | 2017-04-05 | yes | yes |
| 331-237 | Verizon | NAPERVILLE | 2017-11-07 | yes | yes |
| 331-238 | AT&T | DOWNERSGRV | 2017-12-19 | yes | yes |
| 331-239 | Onvoy | YORKVILLE | 2018-08-27 | yes | yes |
| 331-240 | Peerless | W CHICAGO | 2013-04-10 | yes | yes |
| 331-241 | Onvoy | LOMBARD | – | yes | yes |
| 331-242 | T-Mobile | LOMBARD | 2018-10-19 | yes | yes |
| 331-243 | T-Mobile | LOMBARD | 2018-10-19 | yes | yes |
| 331-244 | Onvoy | NAPERVILLE | 2017-09-21 | yes | yes |
| 331-245 | T-Mobile | BARTLETT | 2013-04-18 | yes | yes |
| 331-246 | T-Mobile | LEMONT | 2018-10-19 | yes | yes |
| 331-247 | Vonage | NAPERVILLE | 2018-11-21 | yes | yes |
| 331-248 | Comcast | GENEVA | 2007-07-06 | yes | yes |
| 331-249 | Onvoy | NAPERVILLE | 2018-12-05 | yes | yes |
| 331-250 | T-Mobile | AURORA | 2012-04-10 | yes | yes |
| 331-251 | Verizon | DOWNERSGRV | 2012-12-05 | yes | yes |
| 331-252 | AT&T | WARRENVL | 2016-06-02 | yes | yes |
| 331-253 | T-Mobile | LEMONT | 2014-10-27 | yes | yes |
| 331-254 | T-Mobile | SUGARGROVE | 2014-07-16 | yes | yes |
| 331-255 | Onvoy | AURORA | 2017-08-22 | yes | yes |
| 331-256 | Verizon | AURORA | 2011-09-13 | yes | yes |
| 331-257 | AT&T | AURORA | 2020-01-17 | yes | yes |
| 331-258 | Onvoy | AURORA | – | yes | yes |
| 331-259 | Peerless | SUGARGROVE | – | yes | yes |
| 331-260 | AT&T | DOWNERSGRV | 2019-02-25 | yes | yes |
| 331-261 | T-Mobile | LEMONT | 2019-06-20 | yes | yes |
| 331-262 | T-Mobile | AURORA | 2008-07-30 | yes | yes |
| 331-263 | Onvoy | ITASCA | 2016-03-11 | yes | yes |
| 331-264 | Lumen | HINSDALE | 2020-03-06 | yes | yes |
| 331-265 | Onvoy | GENEVA | – | yes | yes |
| 331-266 | AT&T | ST CHARLES | 2020-04-10 | yes | yes |
| 331-267 | Vonage | LOMBARD | 2020-09-18 | yes | yes |
| 331-268 | T-Mobile | SUGARGROVE | 2021-01-14 | yes | yes |
| 331-269 | T-Mobile | AURORA | 2021-05-14 | yes | yes |
| 331-270 | Onvoy | AURORA | 2021-07-20 | yes | yes |
| 331-271 | Onvoy | HINSDALE | 2020-10-21 | yes | yes |
| 331-272 | Onvoy | ST CHARLES | 2021-07-15 | yes | yes |
| 331-273 | Onvoy | LEMONT | 2021-06-09 | yes | yes |
| 331-274 | T-Mobile | AURORA | 2021-08-03 | yes | yes |
| 331-275 | T-Mobile | BARTLETT | 2021-08-03 | yes | yes |
| 331-276 | Verizon | ST CHARLES | 2014-11-10 | yes | yes |
| 331-277 | AT&T | LOMBARD | 2021-08-06 | yes | yes |
| 331-278 | AT&T | AURORA | 2021-08-13 | yes | yes |
| 331-279 | Windstream | ELMHURST | 2021-10-15 | yes | yes |
| 331-280 | Verizon | DOWNERSGRV | 2021-12-29 | yes | yes |
| 331-281 | AT&T | NAPERVILLE | 2012-10-25 | yes | yes |
| 331-282 | Onvoy | HINSDALE | 2021-12-10 | yes | yes |
| 331-283 | T-Mobile | GENEVA | 2022-02-23 | yes | yes |
| 331-284 | T-Mobile | BARTLETT | 2022-03-11 | yes | yes |
| 331-285 | Verizon | NAPERVILLE | 2022-05-04 | yes | yes |
| 331-286 | Verizon | ST CHARLES | 2022-07-15 | yes | yes |
| 331-287 | Bandwidth | AURORA | 2022-07-20 | yes | yes |
| 331-288 | TON80 COMMUNICATIONS, LLC | ELBURN | 2022-02-17 | yes | yes |
| 331-289 | T-Mobile | HINSDALE | 2022-08-12 | yes | yes |
| 331-290 | Verizon | AURORA | 2022-08-26 | yes | yes |
| 331-291 | Verizon | DOWNERSGRV | 2022-08-26 | yes | yes |
| 331-292 | Charter | DOWNERSGRV | 2022-10-14 | yes | yes |
| 331-293 | AT&T | AURORA | 2023-01-10 | yes | yes |
| 331-294 | Verizon | NAPERVILLE | 2023-01-12 | yes | yes |
| 331-295 | NUSO, LLC | AURORA | 2023-02-07 | yes | yes |
| 331-296 | Dish | WHEATON | 2023-04-18 | yes | yes |
| 331-297 | Onvoy | BATAVIA | 2023-08-09 | yes | yes |
| 331-298 | Onvoy | NAPERVILLE | 2023-08-09 | yes | yes |
| 331-299 | FRACTEL, LLC | HINSDALE | 2021-01-04 | yes | yes |
| 331-300 | T-Mobile | AURORA | 2016-03-17 | yes | yes |
| 331-301 | T-Mobile | AURORA | – | yes | yes |
| 331-302 | Verizon | AURORA | 2013-02-11 | yes | yes |
| 331-303 | Bandwidth | ELBURN | – | yes | yes |
| 331-304 | T-Mobile | BARTLETT | 2015-02-20 | yes | yes |
| 331-305 | Verizon | NAPERVILLE | 2013-08-15 | yes | yes |
| 331-306 | Onvoy | DOWNERSGRV | 2023-09-19 | yes | yes |
| 331-307 | T-Mobile | LOMBARD | 2014-10-13 | yes | yes |
| 331-308 | Bandwidth | BARTLETT | 2014-12-23 | yes | yes |
| 331-309 | COMMIO, LLC | LEMONT | – | yes | yes |
| 331-310 | Bandwidth | BIG ROCK | 2014-12-29 | yes | yes |
| 331-312 | Verizon | AURORA | 2023-11-06 | yes | yes |
| 331-313 | Charter | NAPERVILLE | 2022-08-16 | yes | yes |
| 331-314 | Verizon | ST CHARLES | 2023-11-17 | yes | yes |
| 331-315 | AT&T | LOMBARD | 2016-08-08 | yes | yes |
| 331-316 | COMMIO, LLC | NAPERVILLE | 2024-01-04 | yes | yes |
| 331-317 | COMMIO, LLC | HINSDALE | 2024-01-05 | yes | yes |
| 331-318 | Bandwidth | LEMONT | – | yes | yes |
| 331-319 | Onvoy | AURORA | 2024-01-24 | yes | yes |
| 331-320 | Onvoy | BARTLETT | 2024-01-30 | yes | yes |
| 331-321 | T-Mobile | AURORA | 2015-07-20 | yes | yes |
| 331-322 | Onvoy | LOMBARD | 2024-02-08 | yes | yes |
| 331-323 | Onvoy | GLEN ELLYN | 2024-02-08 | yes | yes |
| 331-324 | Onvoy | YORKVILLE | 2024-03-13 | yes | yes |
| 331-325 | Charter | LEMONT | 2024-03-21 | yes | yes |
| 331-326 | Onvoy | DOWNERSGRV | 2024-03-28 | yes | yes |
| 331-327 | Verizon | ST CHARLES | 2024-11-14 | yes | yes |
| 331-328 | AT&T | NAPERVILLE | 2024-12-16 | yes | yes |
| 331-329 | Onvoy | AURORA | 2025-01-08 | yes | yes |
| 331-330 | AT&T | NAPERVILLE | 2008-08-19 | yes | yes |
| 331-331 | Onvoy | AURORA | 2025-08-21 | yes | yes |
| 331-332 | AT&T | NAPERVILLE | 2008-11-03 | yes | yes |
| 331-333 | AT&T | NAPERVILLE | 2008-11-03 | yes | yes |
| 331-334 | Onvoy | BATAVIA | 2021-06-02 | yes | yes |
| 331-335 | AT&T | ST CHARLES | 2024-04-30 | yes | yes |
| 331-336 | FRACTEL, LLC | AURORA | 2019-10-11 | yes | yes |
| 331-337 | AT&T | OSWEGO | 2025-01-09 | yes | yes |
| 331-338 | Charter | AURORA | 2025-01-29 | yes | yes |
| 331-339 | Verizon | AURORA | 2025-08-28 | yes | yes |
| 331-340 | Onvoy | ITASCA | 2025-11-05 | yes | yes |
| 331-341 | Onvoy | PLANO | 2021-03-30 | yes | yes |
| 331-342 | Verizon | NAPERVILLE | 2025-11-18 | yes | yes |
| 331-343 | Onvoy | DOWNERSGRV | 2023-01-13 | yes | yes |
| 331-344 | Onvoy | W CHICAGO | 2026-02-02 | yes | yes |
| 331-345 | FRACTEL, LLC | NAPERVILLE | 2020-11-18 | yes | yes |
| 331-346 | Verizon | NAPERVILLE | 2026-05-18 | yes | yes |
| 331-347 | Onvoy | WHEATON | 2026-07-28 | yes | no |
| 331-348 | FRACTEL, LLC | ELBURN | 2019-10-11 | yes | yes |
| 331-349 | AT&T | ST CHARLES | 2026-08-14 | yes | no |
| 331-356 | FRACTEL, LLC | BARTLETT | 2019-10-10 | yes | yes |
| 331-373 | TON80 COMMUNICATIONS, LLC | OSWEGO | 2022-02-25 | yes | yes |
| 331-385 | AT&T | AURORA | 2016-09-28 | yes | yes |
| 331-388 | FRACTEL, LLC | SUGARGROVE | 2021-01-25 | yes | yes |
| 331-399 | FRACTEL, LLC | DOWNERSGRV | 2021-01-22 | yes | yes |
| 331-400 | FRACTEL, LLC | OSWEGO | 2019-08-08 | yes | yes |
| 331-401 | Lumen | NAPERVILLE | 2015-12-14 | yes | yes |
| 331-422 | Lumen | ST CHARLES | 2008-11-13 | yes | yes |
| 331-425 | T-Mobile | AURORA | 2007-07-11 | yes | yes |
| 331-426 | TON80 COMMUNICATIONS, LLC | LEMONT | 2022-02-18 | yes | yes |
| 331-431 | Bandwidth | AURORA | 2010-05-26 | yes | yes |
| 331-442 | Verizon | ST CHARLES | 2008-10-30 | yes | yes |
| 331-444 | Verizon | NAPERVILLE | 2010-08-04 | yes | yes |
| 331-452 | Verizon | AURORA | 2007-09-20 | yes | yes |
| 331-454 | AT&T | AURORA | 2009-05-07 | yes | yes |
| 331-456 | FIRST COMMUNICATIONS, LLC | ROSELLE | 2007-12-05 | yes | yes |
| 331-457 | Verizon | NAPERVILLE | 2008-11-14 | yes | yes |
| 331-462 | Verizon | LOMBARD | 2008-08-23 | yes | yes |
| 331-465 | AT&T | W CHICAGO | 2007-10-17 | yes | yes |
| 331-466 | TON80 COMMUNICATIONS, LLC | GLEN ELLYN | 2022-02-17 | yes | yes |
| 331-472 | T-Mobile | NAPERVILLE | 2008-10-22 | yes | yes |
| 331-481 | Verizon | DOWNERSGRV | 2008-10-29 | yes | yes |
| 331-500 | FRACTEL, LLC | GENEVA | 2021-01-04 | yes | yes |
| 331-529 | FRACTEL, LLC | NAPERVILLE | 2019-08-08 | yes | yes |
| 331-551 | AT&T | LOMBARD | 2008-11-05 | yes | yes |
| 331-575 | T-Mobile | AURORA | 2007-09-18 | yes | yes |
| 331-588 | AT&T | ST CHARLES | 2010-02-15 | yes | yes |
| 331-600 | FRACTEL, LLC | WHEATON | 2019-08-08 | yes | yes |
| 331-625 | Verizon | DOWNERSGRV | 2009-10-16 | yes | yes |
| 331-627 | TON80 COMMUNICATIONS, LLC | LOMBARD | 2022-02-25 | yes | yes |
| 331-631 | Charter | DOWNERSGRV | 2022-07-07 | yes | yes |
| 331-642 | Bandwidth | ELMHURST | – | yes | yes |
| 331-643 | T-Mobile | AURORA | 2007-09-18 | yes | yes |
| 331-645 | T-Mobile | ELMHURST | 2007-11-05 | yes | yes |
| 331-666 | Onvoy | AURORA | 2017-09-29 | yes | yes |
| 331-684 | RCN TELECOM SERVICES OF ILLINIOS, INC. - IL | AURORA | 2007-07-12 | yes | yes |
| 331-688 | TON80 COMMUNICATIONS, LLC | NAPERVILLE | 2022-02-17 | yes | yes |
| 331-701 | Verizon | NAPERVILLE | 2014-12-11 | yes | yes |
| 331-702 | Verizon | NAPERVILLE | 2013-10-23 | yes | yes |
| 331-703 | T-Mobile | W CHICAGO | 2013-10-24 | yes | yes |
| 331-704 | Bandwidth | KANEVILLE | 2015-04-21 | yes | yes |
| 331-707 | T-Mobile | AURORA | 2016-08-23 | yes | yes |
| 331-716 | Onvoy | WHEATON | 2016-01-18 | yes | yes |
| 331-717 | AT&T | OSWEGO | 2016-01-18 | yes | yes |
| 331-725 | AT&T | OSWEGO | – | yes | yes |
| 331-732 | FRACTEL, LLC | GENEVA | 2019-10-11 | yes | yes |
| 331-746 | TON80 COMMUNICATIONS, LLC | KANEVILLE | 2022-02-17 | yes | yes |
| 331-757 | T-Mobile | LEMONT | 2016-07-13 | yes | yes |
| 331-758 | FRACTEL, LLC | AURORA | 2021-10-27 | yes | yes |
| 331-771 | Onvoy | ST CHARLES | 2016-02-10 | yes | yes |
| 331-775 | Comcast | DOWNERSGRV | 2016-01-04 | yes | yes |
| 331-777 | Verizon | DOWNERSGRV | 2010-09-22 | yes | yes |
| 331-788 | FRACTEL, LLC | GENEVA | 2021-01-25 | yes | yes |
| 331-800 | Onvoy | W CHICAGO | 2017-09-29 | yes | yes |
| 331-801 | AT&T | DOWNERSGRV | 2014-05-15 | yes | yes |
| 331-803 | Peerless | LEMONT | 2013-04-10 | yes | yes |
| 331-806 | Comcast | WHEATON | 2015-06-11 | yes | yes |
| 331-808 | Bandwidth | PLANO | 2015-06-05 | yes | yes |
| 331-814 | T-Mobile | NAPERVILLE | 2015-06-25 | yes | yes |
| 331-825 | DIGITAL NETWORK ACCESS COMMUNICATIONS, INC. - IL | GENEVA | – | – | yes |
| 331-826 | T-Mobile | ELMHURST | 2008-11-18 | yes | yes |
| 331-837 | TON80 COMMUNICATIONS, LLC | W CHICAGO | 2022-01-07 | yes | yes |
| 331-850 | Onvoy | BIG ROCK | 2021-03-30 | yes | yes |
| 331-866 | TON80 COMMUNICATIONS, LLC | WHEATON | 2022-01-13 | yes | yes |
| 331-867 | FRACTEL, LLC | YORKVILLE | 2020-07-14 | yes | yes |
| 331-871 | Onvoy | W CHICAGO | 2016-02-17 | yes | yes |
| 331-888 | Peerless | WARRENVL | 2010-09-24 | yes | yes |
| 331-899 | FRACTEL, LLC | LOMBARD | 2020-12-22 | yes | yes |
| 331-900 | FRACTEL, LLC | ELMHURST | 2019-08-08 | yes | yes |
| 331-901 | Bandwidth | ST CHARLES | 2015-04-23 | yes | yes |
| 331-903 | AT&T | DOWNERSGRV | 2014-05-15 | yes | yes |
| 331-946 | FRACTEL, LLC | GLEN ELLYN | 2020-07-14 | yes | yes |
| 331-979 | Comcast | ELMHURST | 2015-03-03 | yes | yes |
| 331-980 | T-Mobile | AURORA | 2014-10-13 | yes | yes |
| 331-998 | Verizon | DOWNERSGRV | 2015-09-16 | yes | yes |
| 331-999 | Bandwidth | OSWEGO | 2010-09-22 | yes | yes |
Frequently asked
How many prefixes does area code 331 have?
224 NXX blocks are assigned of 786 possible. Each block is 10,000 consecutive numbers, so the code currently covers about 2,240 thousand-number ranges across 24 rate centers.
What do the first three digits after 331 tell me?
They identify the block, which tells you the rate center it was allocated to and the carrier that received it. They do not tell you who serves the number today: portability moves numbers between carriers, and pooling splits a block between several of them.
Is a 331 prefix tied to a specific town?
To a rate center, which is billing geography rather than a town. NANPA abbreviates rate center names to ten characters and in large metros uses zone codes, so the name is a NANPA label, not a place name.
What does “pooled” mean in the 331 table?
That the block is in thousands-block pooling: carriers draw 1,000-number lots from it instead of taking all 10,000. 223 of 331's blocks are pooled, which is how regulators slowed down area code exhaustion – and why one prefix can belong to several carriers.
Source and limits
NANPA CO Code Assignment Records, all states, utilized codes, file updated 11/01/2026 – the rows where the record's Use field is “AS” (assigned). Unavailable codes are excluded. The records say who received a block and when, not who serves a particular number today.
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