Area code 410 opened in October 1991, according to the FCC. NANPA describes 410 and its first overlay, 443, as the area codes that serve eastern Maryland, a region that takes in Baltimore, Annapolis, and the Eastern Shore. A third code, 667, has shared the same region since March 24, 2012, and every local call there is dialed with ten digits.
Quick answer
- 410 serves Baltimore and eastern Maryland. It opened in October 1991 (FCC).
- 443 joined 410 on the same territory. The FCC lists 443 as opened in June 1997.
- 667 is the third code for the region. The Maryland Public Service Commission (PSC) approved the overlay on January 3, 2001, and 667 numbers could be assigned from March 24, 2012.
- Local calls require ten digits. The PSC says 410 and 443 already had mandatory 10-digit dialing before 667 arrived.
The essentials
410 area code: quick facts
| Area code | 410 |
| Coverage | Baltimore and eastern Maryland, shared with 443 and 667 across the same region |
| State | Maryland |
| Time zone | Eastern Time (ET) |
| Opened | October 1991 |
| Overlay codes on the same territory | 443 (June 1997), 667 (numbers from March 24, 2012) |
| Other Maryland codes | 301, 240, and 227, which serve a separate region |
| Dialing | 10 digits for local calls: 3-digit area code plus 7-digit number |
| Country code | +1, the country code for the North American Numbering Plan |
How 410 became Baltimore's code
- January 1947: Area code 301 opens, according to the FCC. It is the only Maryland code in the FCC table that opened before 1991. NANPA lists 301 as the code 410 was taken from, and gives October 6, 1991 as the 410 in-service date (NANPA).
- October 1991: Area code 410 opens (FCC).
- June 1997: Area code 443 opens (FCC) on the 410 territory. In the same month the FCC lists 240 as opened in Maryland; NANPA lists 240 as an overlay of 301 (NANPA).
- January 3, 2001: The Maryland PSC, in Case No. 8853, issues Order No. 76681 approving an all-services distributed overlay as the relief method for the 410 and 443 codes "that serve eastern Maryland." NANPA assigns 667 for the overlay (NANPA planning letter PL-266, March 14, 2001).
- March 14, 2001: NANPA says the 667 in-service date will be the date the 410/443 numbers run out, then expected to be December 1, 2001.
- August 28, 2001: The PSC issues a notice continuing its rationing plan for the region. NANPA says rationing continues at thirteen codes per month and moves the expected exhaust to the third quarter of 2002 (PL-299, September 4, 2001).
- March 24, 2012: New lines or services may be assigned numbers with the 667 area code (Maryland PSC). The FCC lists 667 as opened in March 2012.
Where area code 410 is used
Because 443 and 667 overlay 410, the three codes share one territory. NANPA's 2001 planning letter calls it the area served by "the 410 and 443 NPAs that serve eastern Maryland," and the Maryland PSC says 667 serves "the same geographic region" as 410 and 443.
The rate center map attached to that letter, dated March 7, 2001, names rate centers in the region including Baltimore, Aberdeen, Annapolis, Bel Air, Cambridge, Catonsville, Chestertown, Columbia, Crisfield, Dundalk, Easton, Elkton, Ellicott City, Glen Burnie, Havre de Grace, Ocean City, Pikesville, Prince Frederick, Princess Anne, Salisbury, Solomons, Towson, and Westminster. A rate center is a billing area, not a boundary, and the map is from 2001. The sources checked do not give a current official map or county list for 410, so confirm a specific address with your phone provider.
Why 410 added codes
Every new code in the region came from demand for numbers. When the PSC approved the 667 overlay in 2001, NANPA expected the 410 and 443 numbers to run out by December 1, 2001. By September 2001 that date had moved to the third quarter of 2002, while the PSC kept rationing new central office codes at thirteen per month. NANPA's letters set the 667 start as the date the 410/443 supply ran out, to be fixed three months ahead. In the end, the PSC says 667 numbers could be assigned from March 24, 2012.
The PSC chose an overlay rather than a split. Under an overlay, existing numbers keep their area code, and new lines can get the new code. The PSC says no lines with 410 or 443 numbers were changed to 667 numbers.
NANPA's April 2026 analysis projects that the 410/443/667 area will run out of numbers in the first quarter of 2036, based on data as of March 1, 2026. Its April 2025 analysis had projected the third quarter of 2034. Forecasts move from one analysis to the next, so treat the date as an estimate.
Area codes around 410
The table shows how each code relates to 410, based on the FCC, NANPA, and PSC sources in this guide. The sources checked do not describe which codes border 410 on every side, so the table does not claim to show every neighbor.
| Code | Where it applies | Relation to 410 |
|---|---|---|
| 410 | Baltimore and eastern Maryland | Opened October 1991 |
| 443 | Same region as 410 | Overlay; opened June 1997 (FCC) |
| 667 | Same region as 410 and 443 | Overlay, numbers from March 24, 2012 |
| 301 | Maryland, opened January 1947 (FCC) | Separate region; NANPA lists it as the code 410 was taken from (NANPA) |
| 240 and 227 | Maryland; opened June 1997 and June 2023 (FCC) | Separate region; NANPA lists 301 as an overlay partner of both (NANPA) |
| 202 | District of Columbia, opened January 1947 (FCC) | Separate jurisdiction |
Code family: splits and overlays
NANPA lists these codes as related to 410, with the date each entered service. A split moves part of a code's area to a new code. An overlay adds a code to the same area.
| Code | Relation to 410 | In service |
|---|---|---|
| 301 | 410 was split from this code | January 1, 1947 |
| 410 | This code | October 6, 1991 |
| 443 | Overlay: shares 410's area | June 1, 1997 |
| 667 | Overlay: shares 410's area | March 24, 2012 |
Source: NANPA NPA report, file dated October 26, 2026.
Overlay codes that share 410's territory
An overlay adds a new area code to the same geographic area, so existing numbers do not change. Two overlay codes now serve eastern Maryland alongside 410:
- 443 (opened June 1997, FCC): the first code added to the 410 region.
- 667 (approved January 3, 2001; numbers from March 24, 2012): the third code for the region.
Because the codes overlap, two neighbors on the same street can have different area codes. The PSC says the price of a call, your coverage area, and other rates and services do not change because of the 667 overlay, and all local calls remain local, regardless of the number of digits dialed.
Time zone and daylight saving time
Area code 410 uses Eastern Time. The tz database lists America/New_York as "Eastern (most areas)". Federal rules (49 CFR 71.4) define the Eastern zone as the part of the United States west of 67°30′ W. longitude and east of the boundary line described in 49 CFR 71.5. Maryland lies within that band.
NIST says daylight saving time begins at 2:00 a.m. on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November. The NIST page lists Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands, and Arizona as places that do not observe it, and Maryland is not on that list. In 2026, NIST gives March 8 and November 1 as the change dates.
When it is 10:00 a.m. in Baltimore
| Where you are | Local time |
|---|---|
| Eastern Time | 10:00 a.m. |
| Central Time | 9:00 a.m. |
| Mountain Time | 8:00 a.m. |
| Pacific Time | 7:00 a.m. |
These differences hold all year, because the Eastern, Central, Mountain and Pacific zones change clocks on the same dates. Arizona does not observe daylight saving time (NIST), so an Arizona clock matches Mountain Time in winter and Pacific Time in summer. A 410 number does not prove the person you are calling is in the Eastern zone, so use the time where the person actually is.
How to dial a 410 number
North American numbers have three parts: a country code, a three-digit area code, and a seven-digit local number. NANPA says the ITU assigned country code 1 to the NANP area. The Maryland PSC says customers with a 410, 443, or 667 number dial the area code for all calls, including calls within the same area code. NANPA's 2001 planning letter describes the Maryland dialing plan: local calls as 10 digits or, permissively, 1 plus 10 digits, and toll calls as 1 plus 10 digits.
The PSC adds that any three-digit number available in your community, such as 211, 311, 411, 511, 611, 711, 811, or 911, can still be dialed with just three digits.
From another country: dial +1 410 followed by the seven-digit number. Country code 1 is assigned to the North American Numbering Plan (NANPA).
Can you text a 410 number? The area code alone does not tell you. Whether a number can receive text messages depends on the number type, the carrier and how the number is registered.
Caller ID and scams with a 410 number
The FTC warns that "Scammers can make any name or number show up on your caller ID." That is called spoofing. Scammers can also match the first six digits of your own number, which the FTC calls neighbor spoofing.
- If you pick up and do not recognize the caller, the FTC advises that you hang up.
- Letting an unknown call go to voicemail is one option.
- The FTC says call blocking is your best defense against unwanted calls.
The sources checked do not say that 410 numbers are targeted more than others. A 410 number shows the code that was assigned, not who is calling or where they are. Because 443 and 667 share the same region, and the region reaches well beyond the city, a 410 caller ID is not a reliable sign that the caller is in Baltimore.
Calling into the 410 area as a business
The rules for a business call depend on where the person you are calling is, not on the area code of their number. Numbers move between providers and phones travel, so a 410 number does not tell you which state's rules apply or what the local time is. NANPA lists the Baltimore area in the Eastern time zone, but the person who answers may be anywhere.
- Calling hours. The FCC rule at 47 CFR 64.1200(c)(1) bars telephone solicitations to a residential subscriber before 8 a.m. or after 9 p.m., measured as "local time at the called party's location." The FTC's Telemarketing Sales Rule, 16 CFR 310.4(c), sets the same 8:00 a.m. to 9:00 p.m. window by the local time at the called person's location.
- Do Not Call. Residential numbers listed on the National Do Not Call Registry are covered by 47 CFR 64.1200(c)(2).
- State rules. Maryland and other states may add their own rules. This guide does not summarize state law. Check with a lawyer or the state attorney general before you run a calling campaign.
This is general information, not legal advice.
Related reading: Do Not Call compliance, predictive dialer compliance in 2026, and STIR/SHAKEN caller ID authentication.
Choosing a 410 number for a business
410 is the oldest code in its region, but the PSC says new lines or services in the region may be assigned a 667 number, and 443 serves the same territory. A new line may carry 443 or 667 instead of 410, and the area code does not show which part of eastern Maryland the business is in.
Because the codes share territory, route calls by team or extension, not by area code. Ask your provider which code a new line gets, since that depends on its current inventory.
Whether a specific 410 number can be assigned to your business depends on your phone provider and its current inventory. This guide does not make claims about availability.
Important: Confirm availability with your provider before you plan a campaign or print a number on materials.
Before you use a 410 number
- Confirm the number is available from your provider, and get its terms in writing.
- Ask who owns the number and whether it can be moved to another provider if you switch.
- Confirm which area code your line uses. 410, 443, and 667 all serve the same region.
- Set 10-digit dialing for numbers in all three codes before you go live, because the PSC says customers there dial the area code for all calls.
- Print the full 10-digit number with the area code on signs, forms, and websites.
- Route calls by team or extension, because 410 and its overlays share one territory.
- Plan for caller ID. A 410 number does not prove who is calling, and neighbor spoofing copies the first six digits of your own number.
Frequently asked questions
Which area is the 410 area code for?
Area code 410 serves Baltimore and eastern Maryland. NANPA describes the 410 and 443 codes as the area codes that serve eastern Maryland, and its 2001 rate center map for the region includes Baltimore, Annapolis, Towson, Columbia, Salisbury, and Ocean City. The FCC lists 410 as opened in October 1991. Area codes 443 and 667 now serve the same region.
Is area code 410 being split or replaced?
No new split of 410 appears in the sources checked for this guide. The Maryland Public Service Commission chose an overlay, 667, in 2001, and the PSC says 667 numbers could be assigned from March 24, 2012. No 410 or 443 numbers were changed to 667. NANPA's April 2026 analysis projects that the 410/443/667 area will run out of numbers in the first quarter of 2036. Projections change with each analysis.
Do I need to dial 10 digits for a 410 number?
Yes. The Maryland PSC says the 410 and 443 area codes already had mandatory 10-digit dialing before 667 arrived, and that customers with a 410, 443, or 667 number dial the area code for all calls, including calls within the same area code. Three-digit numbers such as 911 can still be dialed with three digits.
Does a 410 number mean the caller is in Baltimore?
Not always. The FTC says scammers can make any name or number show up on caller ID, and neighbor spoofing matches the first six digits of your own number. A 410 number shows the code that was assigned, not who is calling or where they are, and 410 covers much more of Maryland than Baltimore.
What time zone is area code 410 in?
Eastern Time. The tz database lists America/New_York as "Eastern (most areas)", and the federal rule for the Eastern zone (49 CFR 71.4) covers the part of the United States east of the boundary line described in 49 CFR 71.5. Daylight saving time starts at 2:00 a.m. on the second Sunday of March and ends at 2:00 a.m. on the first Sunday of November (NIST).
What hours can a business call a 410 number?
For telemarketing calls to a residential line, the FCC and FTC rules set 8 a.m. to 9 p.m. in the local time of the person called. A 410 number does not show where that person is, so use the time where the person actually is. NANPA lists the Baltimore area in the Eastern time zone. States may add rules; this is general information, not legal advice.
Sources (13)
- The New 667 Area Code: Frequently Asked Questions, Maryland Public Service Commission
- NANPA planning letter PL-266, March 14, 2001 (archived copy)
- NANPA planning letter PL-299, September 4, 2001 (archived copy)
- Numbering Resource Utilization in the United States, FCC, Table 6
- About NANPA, archived copy
- 2026-1 NPA Exhaust Analysis, April 2026, NANPA (archived copy)
- 2025-1 NRUF and NPA Exhaust Analysis, April 2025, NANPA (archived copy)
- NPA report, NANPA (file dated October 26, 2026)
- Phone Scams, FTC Consumer Advice
- That's not your neighbor calling, FTC Consumer Alert
- Daylight Saving Time, NIST
- tz database zone table
- 49 CFR 71.4, Eastern zone