Maryland area codes
Maryland uses 6 area codes. The oldest is 301, in service since 1947; the newest is 227, from 2023. Across them 3,733 of 4,716 possible number blocks are allocated, 79.2% of capacity. 240, 443, 301 and 410 are at or past 95%, which is why new numbers there come from overlays rather than the original code. Verizon holds 43.5% of the 3,733 assigned blocks across the state, ahead of AT&T at 12.6%; a further 8.1% sits with CLEC and VoIP holders outside the national carriers. In the 33 days to 30 October 2026, FTC complaints named a Maryland caller ID 2,943 times – 1.3% of all complaints in the window, most often 443 with 803 (98th of 422 nationally). NANPA records 451 rate centers across the state's codes, and local calls take all ten digits.
All 6 codes
| Code | In service | Blocks used | Largest holder | Complaints | Shares area with |
|---|---|---|---|---|---|
| 227 | 2023 | 142/786 | AT&T 30.3% | 70 | 240, 301 |
| 240 | 1997 | 785/786 | Verizon 23.2% | 599 | 227, 301 |
| 301 | 1947 | 784/786 | Verizon 71% | 477 | 227, 240 |
| 410 | 1991 | 783/786 | Verizon 77.5% | 662 | 443, 667 |
| 443 | 1997 | 785/786 | Verizon 29.2% | 803 | 410, 667 |
| 667 | 2012 | 454/786 | Other CLEC / VoIP 27.3% | 332 | 410, 443 |
Block share is share of allocated number blocks, not of subscribers. Complaint counts cover 28 Sep – 30 Oct 2026 and reflect spoofed caller IDs as much as real calls.
How full Maryland’s codes are
A code holds at most 786 blocks of 10,000 numbers each. When a code fills up, the administrator does not reclaim numbers – it adds an overlay, and from then on new numbers in the same area come from the new code.
Full or nearly full
Who holds the number blocks
Counted from every assigned block in the state: 3,733 blocks, each with the holder NANPA recorded for it. Percentages are measured, not estimated.
| Holder | Blocks | Share of Maryland | Largest in |
|---|---|---|---|
| Verizon | 1,622 | 43.5% | 4 codes |
| AT&T | 469 | 12.6% | 1 code |
| T-Mobile | 416 | 11.1% | – |
| Other CLEC / VoIP | 304 | 8.1% | 1 code |
| Windstream | 239 | 6.4% | – |
| Onvoy | 201 | 5.4% | – |
| Lumen | 185 | 5% | – |
| Bandwidth | 88 | 2.4% | – |
| Peerless | 52 | 1.4% | – |
| Comcast | 39 | 1% | – |
| Spok | 37 | 1% | – |
| Charter | 32 | 0.9% | – |
“Other CLEC / VoIP” is not one company: it is every holder outside the national carriers counted together, which is what resellers and app-based numbers look like in the records. This is allocation, not subscribers.
Spam complaints naming Maryland codes
FTC Do Not Call complaints where the caller ID shown was a Maryland number, 28 Sep – 30 Oct 2026 (33 days). Caller IDs on spam calls are routinely faked, so these are complaints about the code, not calls proven to come from it.
How Maryland got its codes
1 in the 1940s, 3 in the 1990s, 1 in the 2010s, 1 in the 2020s. Each code after the first was split off from or overlaid on one already in service.
- 1947 301 goes into service.
- 1991 410 goes into service, split from or overlaid on 301.
- 1997 240 goes into service, split from or overlaid on 301.
- 1997 443 goes into service, split from or overlaid on 410.
- 2012 667 goes into service, split from or overlaid on 443.
- 2023 227 goes into service, split from or overlaid on 301.
Time zones
Maryland is in Eastern time.
Frequently asked about Maryland area codes
How many area codes does Maryland have?
6 in service. They are 227, 240, 301, 410, 443 and 667.
What is the oldest area code in Maryland?
301, in service since 1947. Every later code in the state was split off from or overlaid on an existing one.
What is the newest area code in Maryland?
227, from 2023, overlaying 301.
Is Maryland running out of numbers?
240, 443, 301 and 410 are at or past 95% of capacity, but NANPA has not opened relief planning for them, so no new code is announced.
What time zone is Maryland in?
Eastern time.
Which Maryland area code gets the most spam complaints?
443 – 803 FTC complaints in the 33 days to 30 October 2026, 98th of 422 codes nationally. Those are complaints about the caller ID shown, and spam callers routinely fake a local-looking number, so this says the code is imitated often, not that the calls come from there.
Which carrier holds the most Maryland numbers?
Verizon, with 43.5% of the 3,733 blocks assigned across Maryland, ahead of AT&T at 12.6%. This is allocation of blocks by the numbering administrator, not a count of subscribers – people keep their numbers when they switch carriers.
Do you have to dial 10 digits in Maryland?
Yes. Every code in the state is in an overlay or ten-digit dialing area, so a local call needs the area code too. Dialing seven digits reaches a recording, not a wrong number.
Sources and verification
- NANPA – NPA Database (npa_report.csv), file date 11/01/2026, retrieved Nov 1, 2026
- NANPA – CO Code Assignment Records, All States (utilized), file updated 11/01/2026, retrieved Nov 1, 2026
- FTC – Do Not Call Reported Calls Data, 28 Sep – 30 Oct 2026, retrieved Nov 1, 2026
Figures on this page are counted from those files, not copied from other sites. Spotted an error? Request a correction. How we collect and check: methodology.