Maryland · Eastern Time
240 Area Code
Area code 240 is in Maryland, serving western Maryland and the Washington, D.C. suburbs in Montgomery and Prince George's counties. It is in the Eastern Time zone. It shares its territory with overlay codes 227 and 301, so 10-digit dialing is required.
Last updated October 1, 2026 · Source: NANPA
Where is the 240 area code?
240 is a Maryland area code covering western Maryland and the Washington, D.C. suburbs in Montgomery and Prince George's counties. In the wider directory it sits in the South region.
Cities in the 240 area code
- Frederick
- Rockville
- Gaithersburg
- Germantown
- Silver Spring
- Bethesda
- Hagerstown
- Bowie
- Waldorf
- College Park
- Laurel
- Greenbelt
- Cumberland
- Upper Marlboro
Counties served by 240
Montgomery County, Prince George's County, Frederick County, Washington County, Charles County, Allegany County, St. Mary's County and Garrett County.
240 overlay codes and dialing
The 240 territory is covered by an overlay of 3 area codes: 227, 240, 301. All of them serve the same geographic area, and the original code is 301. Because more than one code covers the same ground, 10-digit dialing is mandatory — you must dial the area code for every local call. New phone lines may be assigned any of these codes.
History of the 240 area code
240 went into service on June 1, 1997 as an overlay of 301, relieving number exhaustion in the Frederick area. Rather than splitting the region, the overlay lets existing customers keep their numbers while new lines draw from the added code. Learn more in our overlay guide.
Is 240 a scam or spam risk?
240 is a legitimate geographic area code, not a premium or toll line, so a call from it costs you nothing extra. That said, scammers frequently spoof real local area codes to look familiar on caller ID. A genuine 240 number on your screen is no guarantee the caller is in Frederick, MD or trustworthy. See spam & scam-risk area codes for how spoofing works and how to respond.
Explore more
See every code in Maryland, compare codes across the South region, or view all Eastern Time codes. You can also browse the 2XX block or the complete numeric list of US area codes.
New to how this all works? Start with how area codes work, then read up on overlays, 10-digit dialing, and spam & scam-risk codes. To check another number, use the area code lookup tool.
Quick answers
240 area code FAQ
Where is the 240 area code?
The 240 area code is in Maryland, covering western Maryland and the Washington, D.C. suburbs in Montgomery and Prince George's counties, in the South region.
What cities are in the 240 area code?
Cities in the 240 area code include Frederick, Rockville, Gaithersburg, Germantown, Silver Spring, Bethesda, Hagerstown, Bowie, Waldorf and College Park.
What time zone is 240 in?
240 is in the Eastern Time zone.
What is the overlay for the 240 area code?
240 shares its territory with 227 and 301. All 3 codes (227, 240, 301) serve the same area, so 10-digit dialing is required for every call.
When did the 240 area code start?
240 went into service on June 1, 1997 as an overlay of 301.
Do I have to dial 10 digits for 240?
Yes. Because 240 is an overlay area, you must dial the full 10-digit number (area code + 7 digits) for every call.
Is 240 a toll-free or premium code?
No. 240 is a standard geographic area code, so calling it costs the same as any local or long-distance call on your plan. Toll-free calls use 800, 888, 877, 866, 855, 844 or 833.