517
Area code
Statusin service
Introduced1947-01-01
JurisdictionMI, US
Local dialing7D
Time zoneEastern
Last verified2026-09-17
Utilization 80.7% of assignable prefixes assigned
As of 09/17/2026
0%639 of ~792 assignable NXX values (200–999 excl. N11)100%
Prefix-level assignment does not equal number-level exhaustion; thousands-block pooling extends capacity. First assignment on record 2001-01-25, most recent 2026-08-28.
Area codes serve rate-center geographies, not municipal boundaries. “MI” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | MICHIGAN BELL TEL CO | 106 | 16.6% |
| 02 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI | 61 | 9.5% |
| 03 | ACD TELECOM, INC. - MI | 56 | 8.8% |
| 04 | OMNIPOINT COMMUNICATIONS MIDWEST OPERATIONS, LLC | 47 | 7.4% |
| 05 | NEW CINGULAR WIRELESS PCS, LLC - IL | 40 | 6.3% |
| 06 | ONVOY, LLCV - MI | 30 | 4.7% |
| 07 | LEVEL 3 COMMUNICATIONS, LLC - MI | 30 | 4.7% |
| 08 | FRONTIER NORTH, INC. - MI | 30 | 4.7% |
| 09 | TELNET WORLDWIDE, INC. | 29 | 4.5% |
| 10 | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MI | 17 | 2.7% |
Important: these are initial assignees from NANPA CO-code records — the carrier a prefix was originally assigned to. Because of number portability, the current serving carrier of any individual number may differ.
Change history
Recorded events for this NPA- 1947-01-01Area code 517 entered service.
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2000-11-21 | PL-251 ↗ | Revised Permissive Dialing Period for the 517 / 989 (MI) NPA Split |
| 2000-10-26 | PL-244 ↗ | 517 NPA Split, Creating 989 NPA (Michigan) |
| 2000-04-20 | PL-226 ↗ | Suspension of Relief in the 517 NPA (Michigan) |