NumberResearchRecent thousands-block assignments
0 blocks assigned in the last 30 days · from the daily NANPA thousands-block report, 09/19/2026
Most carrier growth happens here, not at the prefix level: under number pooling, carriers receive individual 1,000-number blocks (e.g. 626-470-0XXX) within already-assigned prefixes. Assignments are initial assignments — the current serving carrier of individual numbers may differ due to portability.
Most active assignees, all time — NPA 857
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2019-03-27 | 857-856-9XXX | 9000–9999 | Assigned | IP HORIZON LLC | 515J | CAMBRIDGE | MA |
| 2017-06-12 | 857-424-2XXX | 2000–2999 | Assigned | IP HORIZON LLC | 515J | ROXBURY | MA |
| 2017-06-12 | 857-520-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | HYDE PARK | MA |
| 2017-06-12 | 857-773-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | JAMAICA PL | MA |
| 2017-06-08 | 857-386-9XXX | 9000–9999 | Assigned | IP HORIZON LLC | 515J | CHELSEA | MA |
| 2017-06-08 | 857-425-7XXX | 7000–7999 | Assigned | IP HORIZON LLC | 515J | BRIGHTON | MA |
| 2017-06-08 | 857-663-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | DORCHESTER | MA |
| 2017-06-08 | 857-971-9XXX | 9000–9999 | Assigned | IP HORIZON LLC | 515J | CHARLESTN | MA |
| 2016-06-01 | 857-270-9XXX | 9000–9999 | Assigned | IP HORIZON LLC | 515J | CAMBRIDGE | MA |
| 2016-06-01 | 857-336-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | WINTHROP | MA |
| 2016-06-01 | 857-361-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | BROOKLINE | MA |
| 2016-05-27 | 857-262-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | BOSTON | MA |
| 2016-05-27 | 857-520-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | HYDE PARK | MA |
| 2016-05-27 | 857-957-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | BOSTON | MA |
| 2015-03-03 | 857-314-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | MILTON | MA |
| 2015-02-25 | 857-201-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | WINTHROP | MA |
| 2015-02-25 | 857-373-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | BELMONT | MA |
| 2015-02-25 | 857-496-3XXX | 3000–3999 | Assigned | IP HORIZON LLC | 515J | SO BOSTON | MA |
| 2015-02-24 | 857-304-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | WATERTOWN | MA |
| 2015-02-24 | 857-402-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | EASTBOSTON | MA |
| 2013-09-19 | 857-208-7XXX | 7000–7999 | Assigned | IP HORIZON LLC | 515J | BOSTON | MA |
| 2013-07-29 | 857-500-8XXX | 8000–8999 | Assigned | IP HORIZON LLC | 515J | CAMBRIDGE | MA |
| 2013-03-15 | 857-218-1XXX | 1000–1999 | Assigned | IP HORIZON LLC | 515J | BROOKLINE | MA |
| 2013-03-15 | 857-498-6XXX | 6000–6999 | Assigned | IP HORIZON LLC | 515J | BRIGHTON | MA |
| 2013-03-15 | 857-547-7XXX | 7000–7999 | Assigned | IP HORIZON LLC | 515J | JAMAICA PL | MA |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/19/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.