NumberingData
Verified Nov 1, 2026 · Source: NANPA CO Code Assignment Records

Area code 551 prefixes

300 of the 786 possible NXX blocks are assigned in area code 551 (38.2% of capacity), spread across 23 rate centers and 29 holders. The largest holders are ONVOY, LLC - NJ (71 blocks, 23.7%), OMNIPOINT COMMUNICATIONS, INC. - NJ (67 blocks, 22.3%), CELLCO PARTNERSHIP DBA VERIZON WIRELESS - NJ (44 blocks, 14.7%). Grouped by brand, T-Mobile accounts for 72 blocks; brand-attributable holders cover 87% 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 2001-10-17 to 2026-09-03, with 34 blocks handed out in 2021 alone. 295 blocks (98%) 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. 6 assigned blocks (423, 436, 437, 438, 439, 440) are not yet in service: assigned to a carrier but not open for calls, so a caller ID from one is spoofed. 220 were growth assignments – additional blocks to a carrier that had already filled its earlier ones.

300 assigned blocks of 786
23 rate centers
29 holders of record
98% in thousands-block pooling

Largest holders in 551

Holder of record, as NANPA names itBrandBlocksShare
ONVOY, LLC - NJ Onvoy 71 23.7%
OMNIPOINT COMMUNICATIONS, INC. - NJ T-Mobile 67 22.3%
CELLCO PARTNERSHIP DBA VERIZON WIRELESS - NJ Verizon 44 14.7%
NEW CINGULAR WIRELESS PCS, LLC - DC AT&T 27 9%
FRACTEL, LLC – 16 5.3%
BANDWIDTH.COM CLEC, LLC - NJ Bandwidth 15 5%
TON80 COMMUNICATIONS, LLC – 10 3.3%
CABLEVISION LIGHTPATH, INC. - NJ Altice 9 3%
METROPCS, INC. T-Mobile 5 1.7%
LEVEL 3 COMMUNICATIONS, LLC - NJ Lumen 5 1.7%
MCIMETRO ACCESS TRANSMISSION SERVICES LLC Verizon 3 1%
AIRUS, INC. - NJ – 3 1%

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 300 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.

PrefixHolder of recordRate centerAssignedPooledIn service
551-200 Verizon JERSEYCITY 2007-01-12 yes yes
551-201 Onvoy JERSEYCITY 2023-12-11 yes yes
551-202 AT&T CLIFFSIDE 2015-12-30 yes yes
551-203 Verizon JERSEYCITY 2016-03-09 yes yes
551-204 Verizon FAIR LAWN 2014-10-28 yes yes
551-205 AT&T JERSEYCITY 2016-03-14 yes yes
551-206 Verizon FAIR LAWN 2001-12-19 yes yes
551-207 Verizon RAMSEY 2016-04-01 yes yes
551-208 AT&T JERSEYCITY 2002-04-15 – yes
551-209 T-Mobile WYCKOFF 2016-04-01 yes yes
551-210 Verizon DUMONT 2017-06-14 yes yes
551-212 Altice TEANECK 2017-09-28 yes yes
551-213 Onvoy RUTHERFORD 2016-05-09 yes yes
551-214 Onvoy BAYONNE 2015-05-05 yes yes
551-215 AT&T HACKENSACK 2017-10-17 yes yes
551-216 T-Mobile BAYONNE 2016-11-16 yes yes
551-217 T-Mobile RAMSEY 2017-03-13 yes yes
551-218 Verizon RAMSEY 2017-12-08 yes yes
551-219 T-Mobile HACKENSACK 2018-01-26 yes yes
551-220 AIRUS, INC. - NJ JERSEYCITY 2015-08-12 yes yes
551-221 T-Mobile BAYONNE 2002-05-06 yes yes
551-222 Onvoy JERSEYCITY – yes yes
551-223 Bandwidth FAIR LAWN 2014-04-07 yes yes
551-224 Onvoy FAIR LAWN 2014-05-19 yes yes
551-225 Bandwidth JERSEYCITY 2014-06-02 yes yes
551-226 Verizon JERSEYCITY 2007-10-17 yes yes
551-227 Lumen JERSEYCITY 2014-06-03 yes yes
551-228 Altice HACKENSACK 2014-07-01 yes yes
551-229 Lumen JERSEYCITY 2015-07-20 yes yes
551-230 Onvoy ENGLEWOOD 2018-02-13 yes yes
551-231 Bandwidth OAKLAND 2015-04-16 yes yes
551-232 T-Mobile BAYONNE 2014-10-01 yes yes
551-233 Lumen JERSEYCITY 2014-10-01 yes yes
551-234 T-Mobile CLIFFSIDE 2016-09-30 yes yes
551-235 Verizon JERSEYCITY 2014-10-03 yes yes
551-236 T-Mobile CLOSTER 2014-11-14 yes yes
551-237 Verizon HACKENSACK 2014-11-19 yes yes
551-238 Verizon FAIR LAWN 2014-11-19 yes yes
551-239 Onvoy CLIFFSIDE 2018-02-27 yes yes
551-240 AT&T UNION CITY 2015-12-30 yes yes
551-241 T-Mobile BAYONNE 2015-09-08 yes yes
551-242 Bandwidth CLIFFSIDE 2014-12-24 yes yes
551-243 Verizon FAIR LAWN 2015-01-20 yes yes
551-244 Verizon HACKENSACK 2015-08-17 yes yes
551-245 Verizon HACKENSACK 2015-01-20 yes yes
551-246 T-Mobile FAIR LAWN 2015-01-21 yes yes
551-247 Bandwidth JERSEYCITY 2015-01-29 yes yes
551-248 AIRUS, INC. - NJ CLOSTER 2015-08-12 yes yes
551-249 Onvoy PARK RIDGE 2016-07-11 yes yes
551-250 T-Mobile FAIR LAWN 2017-01-11 yes yes
551-251 Verizon HACKENSACK 2018-03-22 yes yes
551-252 Verizon RAMSEY 2014-10-09 yes yes
551-253 AIRUS, INC. - NJ KEARNY 2015-02-05 yes yes
551-254 T-Mobile UNION CITY 2015-04-16 yes yes
551-255 Verizon HACKENSACK 2016-02-15 yes yes
551-256 Verizon JERSEYCITY 2015-02-10 yes yes
551-257 T-Mobile UNION CITY 2014-11-14 yes yes
551-258 Bandwidth BAYONNE 2015-04-16 yes yes
551-259 AT&T HACKENSACK 2018-03-08 yes yes
551-260 T-Mobile JERSEYCITY 2018-03-28 yes yes
551-261 Verizon JERSEYCITY 2018-05-10 yes yes
551-262 T-Mobile RAMSEY 2015-02-23 yes yes
551-263 T-Mobile JERSEYCITY 2015-09-08 yes yes
551-264 Lumen RAMSEY 2015-09-15 yes yes
551-265 Verizon HACKENSACK 2002-08-21 yes yes
551-266 Verizon FAIR LAWN 2018-05-29 yes yes
551-267 Verizon JERSEYCITY 2015-09-15 yes yes
551-268 AT&T UNION CITY 2016-05-17 yes yes
551-269 Verizon RAMSEY 2017-11-14 yes yes
551-270 Verizon RAMSEY 2018-06-04 yes yes
551-271 T-Mobile BAYONNE 2020-07-29 yes yes
551-272 Onvoy LEONIA 2016-07-11 yes yes
551-273 Onvoy BAYONNE 2016-05-27 yes yes
551-274 Peerless KEARNY 2016-07-14 yes yes
551-275 Verizon HACKENSACK 2016-07-11 yes yes
551-276 T-Mobile RIDGEWOOD 2016-09-22 yes yes
551-277 Onvoy JERSEYCITY 2017-08-22 yes yes
551-278 Telnyx ORADELL 2016-12-05 yes yes
551-279 T-Mobile RAMSEY 2018-07-11 yes yes
551-280 Bandwidth JERSEYCITY 2018-06-26 yes yes
551-281 AT&T HACKENSACK 2018-07-11 yes yes
551-282 Bandwidth WESTWOOD 2018-07-30 yes yes
551-283 AT&T HACKENSACK 2017-12-27 yes yes
551-284 Onvoy RIDGEWOOD 2018-08-16 yes yes
551-285 Onvoy RUTHERFORD – yes yes
551-286 Altice HACKENSACK 2018-08-24 yes yes
551-287 AT&T HACKENSACK 2018-09-13 yes yes
551-288 Onvoy CLOSTER 2020-09-23 yes yes
551-289 Verizon HACKENSACK 2018-01-16 yes yes
551-290 AT&T KEARNY 2020-10-26 yes yes
551-291 T-Mobile RAMSEY 2018-10-26 yes yes
551-292 Peerless KEARNY 2018-11-01 yes yes
551-293 AT&T HACKENSACK 2018-11-07 yes yes
551-294 Bandwidth RAMSEY 2020-12-11 yes yes
551-295 T-Mobile HACKENSACK 2018-11-26 yes yes
551-296 Lumen OAKLAND 2018-12-12 yes yes
551-297 T-Mobile BAYONNE 2018-12-19 yes yes
551-298 CSC WIRELESS, LLC JERSEYCITY 2019-04-05 yes yes
551-299 T-Mobile FAIR LAWN 2019-01-15 yes yes
551-300 Onvoy UNION CITY 2018-01-19 yes yes
551-301 T-Mobile RUTHERFORD 2018-11-26 yes yes
551-302 Verizon HACKENSACK 2019-04-03 yes yes
551-303 T-Mobile CLOSTER 2019-01-28 yes yes
551-304 AT&T RUTHERFORD – yes yes
551-305 Altice RIDGEWOOD 2019-07-26 yes yes
551-306 T-Mobile UNION CITY 2019-08-12 yes yes
551-307 T-Mobile JERSEYCITY 2020-08-10 yes yes
551-308 Lumen RAMSEY 2018-12-12 yes yes
551-309 NUSO, LLC JERSEYCITY 2020-10-01 yes yes
551-310 Vonage WESTWOOD 2020-07-08 yes yes
551-312 T-Mobile BAYONNE 2020-11-10 yes yes
551-313 Charter CLIFFSIDE 2014-10-24 yes yes
551-314 CORETEL NEW JERSEY, INC. - NJ CLIFFSIDE 2019-03-20 yes yes
551-315 Verizon RAMSEY 2020-11-24 yes yes
551-316 Onvoy CLIFFSIDE 2021-01-08 yes yes
551-317 Onvoy DUMONT 2021-01-27 yes yes
551-318 T-Mobile BAYONNE 2021-05-05 yes yes
551-319 Onvoy WYCKOFF 2018-02-15 yes yes
551-320 Altice RUTHERFORD 2021-05-27 yes yes
551-321 Onvoy PARK RIDGE 2020-07-22 yes yes
551-322 Vonage TEANECK 2021-06-23 yes yes
551-323 T-Mobile UNION CITY 2021-06-30 yes yes
551-324 Telnyx WESTWOOD 2021-07-21 yes yes
551-325 Bandwidth JERSEYCITY 2021-07-27 yes yes
551-326 T-Mobile BAYONNE 2021-08-27 yes yes
551-327 T-Mobile UNION CITY 2021-08-27 yes yes
551-328 T-Mobile JERSEYCITY 2021-09-09 yes yes
551-329 COMMIO, LLC RIDGEWOOD 2021-09-23 yes yes
551-330 T-Mobile CLIFFSIDE 2021-10-06 yes yes
551-331 T-Mobile UNION CITY 2021-10-06 yes yes
551-332 Vonage BAYONNE 2021-10-20 yes yes
551-333 FUSION, LLC CLIFFSIDE 2008-03-25 yes yes
551-334 T-Mobile KEARNY 2021-10-27 yes yes
551-335 T-Mobile HACKENSACK 2021-11-18 yes yes
551-336 FRACTEL, LLC HACKENSACK 2020-02-14 yes yes
551-337 Verizon HACKENSACK 2021-11-22 yes yes
551-338 Verizon JERSEYCITY 2021-11-22 yes yes
551-339 T-Mobile BAYONNE 2021-12-06 yes yes
551-340 T-Mobile HACKENSACK 2019-01-28 yes yes
551-341 T-Mobile FAIR LAWN 2021-12-06 yes yes
551-342 T-Mobile UNION CITY 2021-12-06 yes yes
551-343 T-Mobile BAYONNE 2022-01-27 yes yes
551-344 T-Mobile JERSEYCITY 2022-01-27 yes yes
551-345 FRACTEL, LLC HASBROKHTS 2020-02-14 yes yes
551-346 T-Mobile CLOSTER 2022-01-27 yes yes
551-347 T-Mobile UNION CITY 2022-01-27 yes yes
551-348 FRACTEL, LLC LEONIA 2020-10-14 yes yes
551-349 Verizon JERSEYCITY 2022-01-28 yes yes
551-350 Onvoy JERSEYCITY 2022-06-14 yes yes
551-351 Charter CRAGMERE 2021-01-26 yes yes
551-352 Verizon HACKENSACK 2022-07-08 yes yes
551-353 Bandwidth JERSEYCITY 2022-07-21 yes yes
551-354 Dish HACKENSACK 2022-08-01 yes yes
551-355 Onvoy ENGLEWOOD 2021-01-26 yes yes
551-356 FRACTEL, LLC KEARNY 2020-02-14 yes yes
551-357 Onvoy OAKLAND 2022-09-02 yes yes
551-358 T-Mobile JERSEYCITY 2002-04-16 yes yes
551-359 T-Mobile JERSEYCITY 2022-09-02 yes yes
551-360 Bandwidth LEONIA 2022-09-26 yes yes
551-361 Bandwidth HACKENSACK 2022-10-20 yes yes
551-362 T-Mobile JERSEYCITY 2022-11-09 yes yes
551-363 NUSO, LLC BAYONNE 2022-11-14 yes yes
551-364 T-Mobile BAYONNE 2023-03-23 yes yes
551-365 AT&T KEARNY 2022-12-22 yes yes
551-366 FRACTEL, LLC ENGLEWOOD 2021-10-26 yes yes
551-367 Verizon FAIR LAWN 2023-01-09 yes yes
551-368 T-Mobile HACKENSACK 2023-01-09 yes yes
551-369 Bandwidth TEANECK 2023-01-20 yes yes
551-370 T-Mobile RIDGEWOOD 2019-01-28 yes yes
551-371 NUSO, LLC JERSEYCITY 2023-02-09 yes yes
551-372 Onvoy KEARNY 2023-03-01 yes yes
551-373 Onvoy UNION CITY 2023-03-14 yes yes
551-374 Onvoy DUMONT 2023-05-24 yes yes
551-375 T-Mobile UNION CITY 2023-06-29 yes yes
551-376 T-Mobile JERSEYCITY 2023-09-11 yes yes
551-377 Onvoy UNION CITY 2023-09-18 yes yes
551-378 T-Mobile CLIFFSIDE 2023-09-20 yes yes
551-379 Onvoy CLIFFSIDE 2023-09-21 yes yes
551-380 Onvoy RUTHERFORD 2023-09-21 yes yes
551-381 Onvoy RUTHERFORD 2020-07-22 yes yes
551-382 Onvoy ENGLEWOOD 2023-09-21 yes yes
551-383 Onvoy ORADELL 2023-09-21 yes yes
551-384 T-Mobile UNION CITY 2023-10-11 yes yes
551-385 Altice WYCKOFF 2023-11-09 yes yes
551-386 AT&T RIDGEWOOD 2023-12-18 yes yes
551-387 Altice JERSEYCITY 2023-12-07 yes yes
551-388 FRACTEL, LLC BAYONNE 2020-10-14 yes yes
551-389 T-Mobile BAYONNE 2024-01-12 yes yes
551-390 Onvoy PARK RIDGE 2024-02-16 yes yes
551-391 Onvoy TEANECK 2024-03-08 yes yes
551-392 T-Mobile BAYONNE 2024-03-13 yes yes
551-393 AT&T HACKENSACK 2024-05-09 yes yes
551-394 Onvoy HASBROKHTS 2024-05-15 yes yes
551-395 Onvoy CLOSTER 2024-05-29 yes yes
551-396 T-Mobile BAYONNE 2024-06-28 yes yes
551-397 AT&T HACKENSACK 2024-07-30 yes yes
551-398 Onvoy WESTWOOD 2024-07-31 yes yes
551-399 T-Mobile BAYONNE 2017-12-15 yes yes
551-400 Onvoy CRAGMERE 2019-07-19 yes yes
551-401 AT&T UNION CITY 2024-08-22 yes yes
551-402 Verizon RAMSEY 2018-05-10 yes yes
551-403 T-Mobile BAYONNE 2024-09-18 yes yes
551-404 T-Mobile HACKENSACK 2002-04-16 yes yes
551-405 AT&T HACKENSACK 2024-09-19 yes yes
551-406 Onvoy CLOSTER 2024-10-01 yes yes
551-407 T-Mobile KEARNY 2024-10-02 yes yes
551-408 Onvoy DUMONT 2024-11-07 yes yes
551-409 Onvoy HACKENSACK 2024-11-07 yes yes
551-410 Onvoy RIDGEWOOD 2024-11-08 yes yes
551-412 AT&T HACKENSACK 2024-11-25 yes yes
551-413 AT&T KEARNY 2024-11-25 yes yes
551-414 AT&T JERSEYCITY 2024-12-02 yes yes
551-415 Onvoy LEONIA 2024-12-13 yes yes
551-416 Onvoy CRAGMERE 2025-02-06 yes yes
551-417 Onvoy JERSEYCITY 2025-02-06 yes yes
551-418 Onvoy ORADELL 2025-02-13 yes yes
551-419 Verizon FAIR LAWN 2025-02-14 yes yes
551-420 T-Mobile BAYONNE 2025-04-03 yes yes
551-421 Altice UNION CITY 2025-04-03 yes yes
551-422 Onvoy HACKENSACK 2025-04-16 yes yes
551-423 AT&T HACKENSACK 2025-05-20 yes no
551-424 T-Mobile BAYONNE 2025-06-11 yes yes
551-425 Onvoy RAMSEY 2025-08-13 yes yes
551-426 T-Mobile BAYONNE 2025-08-26 yes yes
551-427 Verizon RAMSEY 2001-12-19 – yes
551-428 Verizon JERSEYCITY 2025-09-03 yes yes
551-429 T-Mobile BAYONNE 2025-10-14 yes yes
551-430 T-Mobile JERSEYCITY – yes yes
551-431 Altice JERSEYCITY 2025-10-14 yes yes
551-433 WAVENATION, LLC HACKENSACK 2025-12-05 yes yes
551-434 Onvoy BAYONNE 2026-01-05 yes yes
551-435 VoIP Innovations BAYONNE 2026-03-16 yes yes
551-436 Onvoy ENGLEWOOD 2026-07-09 yes no
551-437 Onvoy TEANECK 2026-07-09 yes no
551-438 Onvoy UNION CITY 2026-07-27 yes no
551-439 Onvoy HACKENSACK 2026-08-12 yes no
551-440 AT&T HACKENSACK 2026-09-03 yes no
551-444 Verizon FAIR LAWN – yes yes
551-449 Verizon HACKENSACK – yes yes
551-451 Onvoy CLIFFSIDE 2023-01-13 yes yes
551-455 Onvoy FAIR LAWN 2021-01-26 yes yes
551-465 FRACTEL, LLC LEONIA 2020-02-14 yes yes
551-482 AT&T UNION CITY 2002-05-06 yes yes
551-486 Verizon HACKENSACK 2001-12-19 – yes
551-497 Verizon HACKENSACK 2005-06-13 yes yes
551-500 Onvoy RAMSEY – yes yes
551-501 Onvoy ENGLEWOOD 2020-05-29 yes yes
551-502 AT&T RIDGEWOOD 2017-06-09 yes yes
551-525 Onvoy JERSEYCITY 2023-10-16 yes yes
551-529 FRACTEL, LLC UNION CITY 2020-02-14 yes yes
551-550 Onvoy JERSEYCITY 2022-03-21 yes yes
551-551 Onvoy JERSEYCITY 2025-08-19 yes yes
551-552 Onvoy CRAGMERE 2019-12-17 yes yes
551-553 Onvoy ORADELL 2022-08-11 yes yes
551-554 Onvoy JERSEYCITY 2020-02-04 yes yes
551-556 T-Mobile UNION CITY 2002-11-13 yes yes
551-557 BLUEBIRD COMMUNICATIONS, LLC - NJ PARK RIDGE 2018-09-11 yes yes
551-574 AT&T CLIFFSIDE 2002-04-15 – yes
551-579 Verizon RAMSEY 2006-09-21 yes yes
551-580 AT&T KEARNY 2002-05-06 yes yes
551-587 T-Mobile HACKENSACK 2001-10-17 yes yes
551-588 TON80 COMMUNICATIONS, LLC RAMSEY 2022-02-24 yes yes
551-600 FRACTEL, LLC WYCKOFF 2020-05-22 yes yes
551-651 Onvoy OAKLAND 2021-01-26 yes yes
551-655 Verizon JERSEYCITY 2002-08-02 yes yes
551-666 Onvoy BAYONNE – yes yes
551-688 TON80 COMMUNICATIONS, LLC LEONIA 2022-02-18 yes yes
551-689 Verizon JERSEYCITY 2005-06-10 yes yes
551-697 Verizon JERSEYCITY 2005-08-12 yes yes
551-722 T-Mobile HASBROKHTS 2017-12-15 yes yes
551-727 TON80 COMMUNICATIONS, LLC BAYONNE 2022-03-04 yes yes
551-733 TON80 COMMUNICATIONS, LLC RIDGEWOOD 2022-03-01 yes yes
551-751 Onvoy WESTWOOD 2021-01-26 yes yes
551-755 FRACTEL, LLC CLOSTER 2021-08-11 yes yes
551-758 FRACTEL, LLC JERSEYCITY 2020-02-14 yes yes
551-766 TON80 COMMUNICATIONS, LLC RUTHERFORD 2022-03-01 yes yes
551-775 Bandwidth HACKENSACK 2016-06-24 yes yes
551-777 Verizon RAMSEY – yes yes
551-786 FRACTEL, LLC UNION CITY 2020-10-14 yes yes
551-788 TON80 COMMUNICATIONS, LLC PARK RIDGE 2022-02-24 yes yes
551-795 Verizon FAIR LAWN 2006-09-21 yes yes
551-799 TON80 COMMUNICATIONS, LLC UNION CITY 2022-03-04 yes yes
551-800 Onvoy WESTWOOD – yes yes
551-804 T-Mobile WYCKOFF 2001-10-18 yes yes
551-815 Onvoy RIDGEWOOD 2021-01-26 yes yes
551-837 TON80 COMMUNICATIONS, LLC HACKENSACK 2021-03-16 yes yes
551-842 FRACTEL, LLC JERSEYCITY 2021-04-01 yes yes
551-866 TON80 COMMUNICATIONS, LLC CLIFFSIDE 2022-02-04 yes yes
551-888 Peerless UNION CITY 2012-11-19 yes yes
551-899 FRACTEL, LLC HASBROKHTS 2021-08-13 yes yes
551-900 Onvoy DUMONT – yes yes
551-946 FRACTEL, LLC HACKENSACK 2020-10-14 yes yes
551-955 FRACTEL, LLC WYCKOFF 2021-08-11 yes yes
551-966 TON80 COMMUNICATIONS, LLC FAIR LAWN 2022-03-03 yes yes
551-990 MULTIPLE OCN LISTING XXXXXXXXXX 2002-03-06 – yes
551-995 Onvoy OAKLAND 2024-11-20 yes yes
551-996 AT&T HACKENSACK 2007-07-17 yes yes
551-997 Onvoy JERSEYCITY 2024-09-26 yes yes
551-998 T-Mobile JERSEYCITY 2001-10-17 yes yes
551-999 Onvoy HACKENSACK – yes yes

Frequently asked

How many prefixes does area code 551 have?

300 NXX blocks are assigned of 786 possible. Each block is 10,000 consecutive numbers, so the code currently covers about 3,000 thousand-number ranges across 23 rate centers.

What do the first three digits after 551 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 551 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 551 table?

That the block is in thousands-block pooling: carriers draw 1,000-number lots from it instead of taking all 10,000. 295 of 551'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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