The 240 area code is an overlay serving western Maryland and the Washington, D.C. suburbs. Introduced in 1997, it was layered directly on top of the existing 301 area code to meet the explosive demand for phone numbers across Montgomery County, Frederick, and the surrounding region.
Quick Summary of the 240 Area Code
| Area Code | 240 |
| State | Maryland (MD) |
| Region | Western Maryland & Washington, D.C. Suburbs |
| Major Cities | Rockville, Bethesda, Silver Spring, Frederick, Gaithersburg, Germantown, Hagerstown, Bowie, Waldorf, College Park |
| Time Zone | Eastern Time (ET) – EST / EDT |
| Dialing Format | 10-digit dialing required |
Geographic Coverage
The 240 area code shares an identical geographic footprint with 301, covering the Washington suburbs of Silver Spring, Bethesda, and College Park, the Montgomery County cities of Rockville, Gaithersburg, and Germantown, the city of Frederick, and the western panhandle toward Hagerstown and Cumberland. Because it is an overlay rather than a separate region, a 240 number and a 301 number can exist on the same street.
Time Zone
The 240 area code observes Eastern Time (ET). Clocks follow Eastern Standard Time (UTC−5) in winter and shift to Eastern Daylight Time (UTC−4) from mid-March through early November. If you are coordinating a call from the West Coast, remember that this region is three hours ahead of Pacific Time, so a 9:00 AM call in California reaches a 240 number at 12:00 PM local time.
Tip: Business hours across the 240 region generally run 9:00 AM to 5:00 PM Eastern Time, Monday through Friday.
How to Dial a 240 Number
Because area code 240 operates as part of an overlay, 10-digit dialing is mandatory for every local and long-distance call. You must dial the full 10-digit number (240 + the seven-digit line number) even when calling a neighbor across the street. For international callers, dial your country’s exit code, then +1 (the North American country code), then 240, followed by the seven-digit local number.
Scam Alerts for the 240 Area Code
Like every U.S. area code, 240 has been used by scammers who spoof local numbers to appear trustworthy. Residents in Rockville, Bethesda, Silver Spring, Frederick, Gaithersburg, Germantown, Hagerstown, Bowie, Waldorf, College Park should stay alert to the following common tactics:
| Scam Type | What to Watch For |
|---|---|
| IRS / Tax Scams | Threatening calls demanding immediate tax payment via gift cards or wire transfer. |
| Utility Shut-off | Impostors claiming to be BGE or Pepco threatening to cut power. |
| Tech Support Fraud | Pop-ups or calls claiming your computer is infected and asking for remote access. |
| Prize / Lottery Scam | Calls saying you won a prize but must pay a “fee” or “tax” to claim it. |
If you receive a suspicious call from a 240 number, take these steps to protect yourself:
- Do not share personal information such as Social Security numbers, bank details, or passwords over the phone.
- Hang up and verify by calling the organization back using an official number from its website.
- Report the call to the FTC at reportfraud.ftc.gov and to the Maryland Attorney General’s Office.
- Block the number and consider registering with the National Do Not Call Registry.
Red Flag: Legitimate agencies such as the IRS, Social Security Administration, or your utility company (BGE, Pepco, or Potomac Edison) will never demand immediate payment by gift card, wire transfer, or cryptocurrency. Any 240 caller making such a demand is a scammer.
History and Economy of the 240 Region
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The 240 area code entered service in 1997 as an overlay for the entire 301 region. Overlays let regulators add a fresh supply of phone numbers to a crowded area without forcing existing customers to change their established numbers. Rather than splitting the map, they simply layered 240 on top of 301, so the two codes share the same cities, employers, and neighborhoods. The area is dominated by the federal government and the sciences: the National Institutes of Health, the FDA, and the biotechnology corridor along Interstate 270 make Montgomery County one of the country’s premier research hubs, while Frederick and the western panhandle add life-sciences and manufacturing employment. Newer phone lines and recently activated mobile numbers in the DC suburbs are especially likely to carry the 240 prefix.
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Looking Up a 240 Number
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To identify a 240 caller, use a reverse phone lookup or search the complete 10-digit number online. Because 240 is a newer code, some numbers may have a smaller public footprint, so exercise extra caution and never share personal or financial details with an unverified caller.
Nearby & Related Area Codes
Maryland is served by several area codes. If you are researching 240, these neighboring and overlay codes are worth knowing:
- 301 – DC suburbs (overlay partner)
- 410 – Baltimore & Eastern Maryland
- 443 – Baltimore overlay
- 667 – Baltimore overlay
You can also browse our full directory of Maryland area codes for more regional guides.
↑ See the complete list of All US Area Codes by State – every area code across all 50 states in one directory.
Explore Neighboring States
Researching area codes just across the state line? Start with these codes in the states that border Maryland:
- Pennsylvania – area code 215
- Delaware – area code 302
- Virginia – area code 804
- West Virginia – area code 304
Frequently Asked Questions
Where is the 240 area code located?
The 240 area code serves western Maryland and the Washington, D.C. suburbs as an overlay of the 301 area code, covering Montgomery County, Frederick, and the western panhandle.
Why does 240 cover the same area as 301?
240 is an overlay code added in 1997 because the 301 region ran short of available phone numbers. Both codes serve the exact same geographic area.
Do I have to dial 10 digits for 240?
Yes. Overlay area codes like 240 always require 10-digit dialing for local calls.
Is the 240 area code Eastern Time?
Yes, the 240 area code follows Eastern Time (EST/EDT), like all of Maryland.
Related 240 Guides
- Is a 240 call safe? Read Is area code 240 a scam? Spam & safety guide.
- Local coverage: see the Frederick area code guide.
- Worried about spam or robocalls? Browse our Scam Alerts directory.