The 240 area code covers the same area as 301, including Washington, D.C. suburbs, Frederick and 41 more places in Maryland.
Area code 240 is in Maryland, on Eastern Time. In the 240 area, phone numbers are given out most in Frederick County, then Montgomery and Charles counties. It has been in service since June 1, 1997. 227 and 301 cover the same area, so two neighbours can have different area codes.
- Where
- 8 counties in Maryland, mostly Frederick County, Montgomery County and Charles County
- Time zone
- Eastern Time
- In service since
- June 1, 1997
- Shares its area with
- 227 (since 2023) and 301 (since 1947)
- Prefixes in use
- 785
- How to dial
- Local calls need all 10 digits: 240-555-0142.
Find out who called you from a 240 number.
Enter the full 10-digit number to see who it is listed to and the city and state on the listing. It is the same free check as our who called me lookup. To see only the caller ID name on the number, use our free CNAM lookup. To see whether it is a mobile, a landline or a VoIP line, use our free VoIP checker. To see which carrier a (240) number is on today, use our free carrier lookup.
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Washington, D.C. suburbs holds 43% of the phone prefixes in area code 240.
A prefix is the three digits after the area code, and NANPA assigns each one to a town. Counting the 785 prefixes in use shows where 240 numbers are actually given out.
- Washington, D.C. suburbs340 prefixes, 43%
- Laurel55 prefixes, 7%
- Frederick43 prefixes, 5%
- Gaithersburg40 prefixes, 5%
- Hagerstown33 prefixes, 4%
- Ashton30 prefixes, 4%
- Waldorf26 prefixes, 3%
- Leonardtown17 prefixes, 2%
Also served: Damascus, Leonardtown, Myersville and Oakland and 31 smaller places.
T-Mobile holds the most phone number prefixes in area code 240: 117 of 785.
NANPA, which runs the North American numbering plan, assigns each prefix (the three digits after the area code) to one carrier. Here is how the 785 prefixes in use in 240 divide between carriers; holders this page does not name are grouped as other carriers.
| Carrier | Prefixes | Share |
|---|---|---|
| T-MobileMobile network | 117 | 15% |
| AT&T MobilityMobile network | 69 | 9% |
| PAETEC (Windstream)Windstream's business phone network | 63 | 8% |
| Level 3 (Lumen)Lumen's business and wholesale network | 62 | 8% |
| Peerless NetworkWholesale phone carrier | 42 | 5% |
| BandwidthSupplies numbers to VoIP and app-based phone services | 35 | 4% |
| 33 other carriers | 397 | 51% |
93% of these prefixes are pooled, which means the blocks of 1,000 numbers inside them can belong to other carriers. Any number can also have been moved to another carrier since, so this shows who holds the prefixes, not who serves a given number.
Want the carrier of one exact number? Our free carrier lookup checks it, because numbers move between carriers.
Source: NANPA central office code assignments, October 1, 2026.
240 started in 1997 as an overlay on 301, and its ground has not changed since.
1997
240 starts on June 1, 1997, as an overlay on 301: new numbers on the same ground.
A 240 number on your screen can still be a scam, because caller ID is easy to fake.
- Let an unknown call go to voicemail. A real caller leaves a message; a robocaller usually does not.
- Look the number up with the box above before you call back, because calling back tells a robocaller your line is live.
- Hang up on anyone who wants gift cards, crypto or a wire transfer, or asks you to read out a code that was just texted to you.
- Report unwanted robocalls at reportfraud.ftc.gov, or paste a suspicious message into our free scam checker.
The area codes closest to 240 are 703, 202 and 717.
This list measures the distance between the centres of each area, across state lines, and shows codes that share one area together.
Maryland has 5 other area codes.
These are the questions people ask most about area code 240.
Where is area code 240?
240 covers Washington, D.C. suburbs, Frederick, Gaithersburg and Laurel and 39 more places in Maryland. In the 240 area, phone numbers are given out most in Frederick County, then Montgomery and Charles counties.
What state is area code 240 in?
Maryland. 240 is a Maryland area code on Eastern Time.
What cities use area code 240?
The places holding the most 240 prefixes are Washington, D.C. suburbs, Frederick, Gaithersburg, Laurel, Waldorf, Hagerstown, Cumberland and Ashton, out of 43 places in all. The count comes from NANPA's prefix assignments as of October 1, 2026.
Which phone company owns area code 240?
No single phone company owns 240. NANPA's records show T-Mobile holds the most 240 prefixes, 117 of 785, followed by AT&T Mobility and PAETEC (Windstream). Numbers move between carriers, so check one exact number with a carrier lookup.
What time zone is area code 240 in?
240 is on Eastern Time.
When did area code 240 start?
240 went into service on June 1, 1997, as an overlay on 301: new numbers for the same area.
Is 240 the same area as 227 and 301?
Yes. 227 (since 2023) and 301 (since 1947) cover the same ground as 240. Nobody's number changed when they were added; new lines simply get whichever code has numbers left, so two neighbours can have different codes.
How do I dial a 240 number?
Local calls need all 10 digits: 240-555-0142.
Is 240 a toll-free number?
No. 240 is a regular area code for Washington, D.C. suburbs and Frederick in Maryland, not a toll-free one. The toll-free codes in North America are 800, 833, 844, 855, 866, 877 and 888.
What area codes are near 240?
The closest are 703/571 (Washington, D.C. suburbs, Virginia), 202/771 (Washington, D.C.), 717/223 (Harrisburg, Pennsylvania) and 410/443/667 (Baltimore, Maryland), measured between the centres of each area.
Who called me from a 240 number?
Enter the full 10-digit number in the lookup above. It returns the listed owner where there is a public record, where the number is registered, and whether it is a mobile, a landline or a VoIP line.
Is area code 240 a scam?
240 is a real Maryland area code, so the code itself is not a warning sign. Scam callers fake local-looking numbers on purpose, so judge the call by what the caller asks for, and look the number up before calling back.
Put this lookup on your site: our free area code widget takes two lines of code and shows any US area code's state, time zone and local time.
Source: NANPA, the North American Numbering Plan Administrator: its area code database and prefix assignments, as of October 1, 2026.