NumberResearchThousands-blocks in 503-374
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/19/2026
The ten 1,000-number thousand-blocks inside prefix 503-374 and who was initially assigned each. Under pooling these blocks often belong to different carriers — the single prefix-level “assignee” is usually just the pool / code holder, not who holds the numbers. ← all 503 blocks
Most active assignees, all time — NPA 503
New assignments by month
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 503-374-0XXX | 0000–0999 | Reserved | LEVEL 3 COMMUNICATIONS, LLC - OR | 3234 | TILLAMOOK | OR |
| 2004-12-15 | 503-374-1XXX | 1000–1999 | Assigned | LEVEL 3 COMMUNICATIONS, LLC - OR | 3234 | TILLAMOOK | OR |
| 2018-01-03 | 503-374-2XXX | 2000–2999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| 2018-01-03 | 503-374-3XXX | 3000–3999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| 2018-01-03 | 503-374-4XXX | 4000–4999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| 2017-09-29 | 503-374-5XXX | 5000–5999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| 2017-09-29 | 503-374-6XXX | 6000–6999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| 2013-11-14 | 503-374-7XXX | 7000–7999 | Assigned | CENTURYLINK COMMUNICATIONS, LLC | 508J | TILLAMOOK | OR |
| 2017-08-15 | 503-374-8XXX | 8000–8999 | Assigned | T-MOBILE USA, INC. | 6529 | TILLAMOOK | OR |
| — | 503-374-9XXX | 9000–9999 | Reserved | LEVEL 3 COMMUNICATIONS, LLC - OR | 3234 | TILLAMOOK | OR |
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.