Area Code 240

About Area Code 240

Area code 240 is a geographic telephone area code assigned to Silver Spring, Maryland. It operates in the Eastern time zone and was first introduced in 1997. Overlay for 301. Western Maryland and D.C. suburbs.

Within Maryland, area code 240 shares numbering capacity with 4 other area codes. The state's 6,180,253-person population (2023 Census Bureau estimate) is served by a combined 5 active codes, with 240 primarily responsible for the Silver Spring region. Maryland's state capital is Annapolis, and its largest city is Baltimore.

When you receive a call from a 240 number on your Caller ID, the call originated from a phone number assigned to the 240 area code — but be aware that Local Number Portability (in effect since 2003) means the caller could be physically located anywhere in the US or Canada. Area code 240 only confirms where the number was originally assigned.

Where is the 240 area code located?

Area code 240 is assigned to Silver Spring, Maryland, in the Eastern time zone. The state of Maryland uses 5 active area codes, and 240 is one of them. Calls placed from the 240 area code originate from numbers assigned by NANPA — the North American Numbering Plan Administrator — and the 240 prefix appears on Caller ID for both landline and wireless calls placed from this region.

The Eastern time zone observes Daylight Saving Time, shifting from UTC-5 to UTC-4 in summer. The local time shown above is always current, so you can quickly check whether it's a reasonable hour to call back.

What cities and counties use the 240 area code?

The 240 area code serves 10 notable cities, listed below in order of population. The largest city in the 240 territory is Silver Spring (81,816 residents in Unknown County).

• Silver Spring, MD — 81,816 residents (6.4% of 240 numbers)
• Baltimore, MD — 565,239 residents (44.2% of 240 numbers)
• Columbia, MD — 104,251 residents (8.1% of 240 numbers)
• Germantown, MD — 91,765 residents (7.2% of 240 numbers)
• Waldorf, MD — 81,410 residents (6.4% of 240 numbers)
• Glen Burnie, MD — 69,260 residents (5.4% of 240 numbers)
• Ellicott City, MD — 75,947 residents (5.9% of 240 numbers)
• Frederick, MD — 79,858 residents (6.2% of 240 numbers)
• Dundalk, MD — 63,057 residents (4.9% of 240 numbers)
• Rockville, MD — 67,117 residents (5.2% of 240 numbers)

Phone number format in area code 240

All phone numbers within area code 240 follow the standard North American 10-digit format:(240) NXX-XXXX. The NXX is the central office prefix (also called an "exchange") and XXXX is the subscriber line number. For long-distance calls within the NANP, dial 1 + 240 + NXX + XXXX. From outside North America, dial your country's international access code, then 1 (the NANP country code), then the 10-digit number.

If you need to verify whether a specific 240 number is wireless, landline, or VoIP, you can use our reverse phone lookup tool. Be aware that number portability means the area code no longer guarantees the caller's physical location — only where the number was first assigned.

History of area code 240

Overlay for 301. Western Maryland and D.C. suburbs.

The original 86 area codes were assigned by AT&T and Bell Labs in 1947 as part of the North American Numbering Plan. At the time, rotary-dial phones meant codes with lower digits (like 212 for NYC, 213 for LA, 312 for Chicago) were given to the largest cities because they took less time to dial. Today's area code assignments still reflect those early choices, even though touch-tone and cell phones made the original reason obsolete.

Is the 240 area code safe to answer?

Area code 240 itself is a normal geographic code with no elevated spam risk. That said, scammers can spoof any area code — including 240 — so if you don't recognize the full number, let it go to voicemail and verify the caller's identity before calling back.