Phone numbers in Mill Valley, California
Mill Valley has 23 phone prefixes in area codes 415, 628.
Biggest holders: AT&T (local phone), Bandwidth, Fractel. This is the local calling area (rate center) where those prefixes were first assigned.
- Mobile carrier 9%
- Local phone company 26%
- Internet / business phone carrier 61%
- Phone company 4%
Every prefix in Mill Valley
Search the first six digits of a number in this list. If it's here, the number started in Mill Valley with the carrier shown. If it isn't, check the California page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 415-322 | Bandwidth | Internet / business phone carrier | – |
| 415-326 | Bandwidth | Internet / business phone carrier | – |
| 415-360 | MCImetro (Verizon Business) | Internet / business phone carrier | – |
| 415-380 | AT&T (local phone) | Local phone company | – |
| 415-381 | AT&T (local phone) | Local phone company | – |
| 415-383 | AT&T (local phone) | Local phone company | – |
| 415-384 | AT&T (local phone) | Local phone company | – |
| 415-388 | AT&T (local phone) | Local phone company | – |
| 415-389 | AT&T (local phone) | Local phone company | – |
| 415-569 | Tpx Communications | Internet / business phone carrier | – |
| 415-634 | Onvoy | Internet / business phone carrier | – |
| 415-843 | MCImetro (Verizon Business) | Internet / business phone carrier | – |
| 415-877 | MetroPCS (T-Mobile) | Mobile carrier | 2001 |
| 415-879 | MetroPCS (T-Mobile) | Mobile carrier | 2001 |
| 415-888 | Comcast | Internet / business phone carrier | – |
| 415-968 | Level 3 (Lumen) | Internet / business phone carrier | 2005 |
| 628-215 | Bandwidth | Internet / business phone carrier | 2016 |
| 628-245 | Onvoy | Internet / business phone carrier | 2016 |
| 628-257 | Race Telecommunications | Phone company | 2016 |
| 628-288 | Fractel | Internet / business phone carrier | 2019 |
| 628-291 | Voip Innovations | Internet / business phone carrier | 2023 |
| 628-477 | Fractel | Internet / business phone carrier | 2021 |
| 628-677 | Fractel | Internet / business phone carrier | 2021 |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number. Source: NANPA central office code records, 2026-10-10.