A historic city of “clustered spires” at the gateway to Western Maryland, Frederick blends a beautifully preserved downtown with a growing biotech economy anchored by Fort Detrick. It is covered by the 301 code and its overlay. This guide breaks down Frederick’s 301 and 240 codes, the required 10-digit dialing, major ZIP codes, and local scam warnings.
Frederick Area Codes at a Glance
| Detail | Information |
|---|---|
| Primary Area Code(s) | 301 |
| Overlay Area Code(s) | 240 |
| Time Zone | Eastern Time (ET) – EST / EDT |
| Major County | Frederick County |
| Region | Western Maryland |
| Dialing Format | 10-digit dialing required |
Area Code Breakdown & Regional Mapping
301 – Western MD & DC Suburbs Code
Area code 301 is one of the original 1947 codes and covers Western Maryland and the Washington, D.C. suburbs, including Frederick, Rockville, and Hagerstown. It is Frederick’s primary code and anchors Frederick County.
240 – Western MD & DC Suburbs Overlay
Area code 240 is the 1997 overlay for the 301 region, sharing the same western-Maryland and DC-suburbs geography. Many newer Frederick lines carry a 240 prefix, fully local to existing 301 numbers.
Neighborhoods & Local Coverage
Frederick’s 301/240 codes cover a city centered on a celebrated Historic District, where the Carroll Creek Linear Park promenade winds past shops, galleries, and restaurants beneath the church steeples that inspired the “clustered spires” nickname. Baker Park and its bell tower anchor the western edge of downtown.
Beyond downtown, the same codes reach the commercial Golden Mile corridor, the Worman’s Mill and Whittier communities, and the research campuses around Fort Detrick and the biotech corridor. As the gateway to Western Maryland, the 301/240 codes tie Frederick to Hagerstown and the mountains to the west.
Local Dialing Rules & International Format
Frederick and the 301 region have required 10-digit dialing since the 240 overlay launched — always dial the area code plus the 7-digit number. Baltimore to the east uses a separate complex, 410/443/667.
Frederick is in the Eastern Time Zone (EST/EDT), like all of Maryland. To call the city from outside the United States, dial your country’s exit code, then the U.S. country code +1, followed by the 10-digit number (for example, +1 301 XXX-XXXX). From inside the U.S. and Canada, simply dial 1 before the 10-digit number for long-distance calls.
Major ZIP Codes Covered
The 301 service area spans many of Frederick’s core ZIP codes, including 21701, 21702, 21703, and 21704.
Spam & Scam Call Warnings in Frederick
Frederick residents report neighbor-spoofing robocalls faking a local 301 prefix, plus fake utility-shutoff threats from callers posing as Potomac Edison. Auto-warranty and Medicare scams are also common across Frederick County.
| Scam Type | What to Watch For |
|---|---|
| Neighbor Spoofing | Calls that mimic a local 301 prefix to look familiar. |
| Utility / Toll Scams | Threats to shut off power or demand toll payment via gift cards. |
| IRS / Government | Robocalls claiming legal action — agencies never call to demand instant payment. |
Red flag: Any caller who pressures you to pay immediately with gift cards, wire transfers, or cryptocurrency is almost certainly running a scam. Hang up and verify through an official number.
↑ See the complete list of All US Area Codes by State for every code across the country.
Nearby & Related Maryland Cities
Frequently Asked Questions
What area code is Frederick, MD?
Frederick uses area code 301 and its overlay 240, shared across Western Maryland and the DC suburbs.
Is 240 a real Maryland area code?
Yes. 240 is the FCC-approved overlay for the 301 region, added in 1997 to expand number capacity across western Maryland and the Washington suburbs.
Do I need to dial 10 digits in Frederick?
Yes. With the 240 overlay active, all local calls in the 301 region require 10-digit dialing.
What time zone is Frederick in?
Frederick observes Eastern Time (EST/EDT), like all of Maryland.
Stay Safe & Explore More
- Verify an unknown caller in our Scam Alerts directory.
- Comparing nationwide numbers? See our Toll-Free Numbers guides.