443
Area code
MD
United States geographic area code, in service since 1997-06-01. Part of the 410/443/667 overlay complex — ten-digit dialing required.
Statusin service
Introduced1997-06-01
JurisdictionMD, US
Local dialing10D
Time zoneEastern
Last verified2026-09-17
Utilization 101% of assignable prefixes assigned
As of 09/17/2026
0%800 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 2001-01-10, most recent 2023-11-21.
Area codes serve rate-center geographies, not municipal boundaries. “MD” identifies the jurisdiction, not an exact city footprint.
Top assignees
Ranked by assigned prefixes · initial assignee ≠ current carrier| Rank | Assignee | Prefixes | Share |
|---|---|---|---|
| 01 | PAETEC ITEL, LLC | 153 | 19.1% |
| 02 | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MD | 121 | 15.1% |
| 03 | OMNIPOINT COMMUNICATIONS CAP OPERATIONS, LLC | 94 | 11.8% |
| 04 | NEW CINGULAR WIRELESS PCS, LLC - DC | 71 | 8.9% |
| 05 | LEVEL 3 COMMUNICATIONS, LLC - MD | 69 | 8.6% |
| 06 | VERIZON MARYLAND, INC. | 56 | 7% |
| 07 | TELEPORT COMMUNICATIONS AMERICA, LLC - MD | 48 | 6% |
| 08 | MCIMETRO ACCESS TRANSMISSION SERVICES LLC | 46 | 5.8% |
| 09 | CORE COMMUNICATIONS, INC.- MD | 34 | 4.3% |
| 10 | METROPCS, INC. | 25 | 3.1% |
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- 1997-06-01Area code 443 entered service (created from 410).
Planning letters & orders
Primary documents| Date | Document | Subject |
|---|---|---|
| 2011-10-10 | PL-427 ↗ | NPA Code 667 to Overlay NPA Code 410/443 (Maryland) |
| 2001-09-04 | PL-299 ↗ | Rationing in NPAs 410, 443, and 667 (Maryland) |
| 2001-03-14 | PL-266 ↗ | NPA 667 to Overlay NPAs 410 and 443 (Maryland) |
| 1996-06-21 | IL-96-06-008 ↗ | NANP-Overlay of 410 (Maryland) Numbering Plan Area (NPA) |