Area Code 301
Maryland
Area code 301 serves Maryland, primarily Columbia, in the Eastern Time (ET) time zone. It has served the region since 01-Jan-1947.
Overlay Area Codes
This area code is part of an overlay region, meaning the same geographic area is served by multiple area codes. Overlay codes were introduced to meet growing demand for phone numbers without requiring existing customers to change their numbers.
This area code shares its geographic region with: area code 227 (Columbia), area code 240 (Columbia).
In service since: 01-Jan-1947
Historical Timeline of Area Code 301
Area code 301 was created on January 1, 1947 as one of the original 86 area codes in the North American Numbering Plan, covering the entire state of Maryland. It has undergone three major changes: a 1991 split creating area code 410 for Baltimore and the Eastern Shore, a 1997 overlay adding area code 240 as Maryland's first overlay, and a 2023 overlay adding area code 227, bringing the total to three area codes sharing the same western Maryland and DC suburban territory. Source: Wikipedia
Key milestones:
- 1947: Created as one of the original 86 area codes covering all of Maryland (NANPA / AT&T Bell System)
- October 6, 1991: 410 split removed Baltimore and Eastern Shore. 301 retained DC suburbs and western Maryland. Permissive dialing extended until November 1, 1992 (NANPA IL 90-12-049)
- June 1, 1997: 240 overlay added as Maryland's first overlay area code. Mandatory 10-digit dialing implemented (NANPA IL 96-06-009)
- January 3, 2001: Maryland PSC Case No. 8853 approved all-services distributed overlay framework for 240/301, reserving 227 for future use
- August 3, 2022: Maryland PSC approved implementation of 227 overlay after NANPA petition. Estimated 240/301 exhaust in Q2 2023 (Maryland PSC)
- June 14, 2023: 227 area code went into service as second overlay for the 301/240 region (Maryland PSC)
The 301 area code has served the Washington DC metropolitan suburbs and western Maryland for nearly 80 years. The 1991 split was driven by exhaust pressure from the growing Baltimore region, while the 1997 and 2023 overlays addressed continued growth in the DC suburban corridor.
Unique Facts About Area Code 301
Area code 301 has several characteristics within the North American Numbering Plan. Source: Wikipedia
- 21 years between approval and activation: Area code 227 was approved by Maryland PSC in Case No. 8853 on January 3, 2001, but did not go into service until June 14, 2023, a gap of over 21 years. This is one of the longest known intervals between regulatory approval and activation of an area code in US numbering plan history (Maryland PSC)
- Projected exhaust in Q1 2041: According to NANPA's 2024-2 NPA Exhaust Projections, the combined 301/240/227 numbering plan area is expected to run out of assignable central office codes in the first quarter of 2041, providing approximately 15 years of headroom from the 2024 analysis (NANPA 2024-2 NPA Exhaust Projections)
- One of the original N0X format codes: Area code 301 was assigned using the N0X format (first digit N, second digit 0, third digit X) reserved for single-NPA states in the original 1947 plan. Maryland was one of only a handful of states that originally had a single area code (NANPA historical records)
- LATA-based boundary definition: The 301/240/227 numbering plan area is defined by two Local Access and Transport Areas: the Washington and Hagerstown LATAs. This explains why portions of Frederick, Howard, Carroll, and Anne Arundel counties were split between 301 and 410 during the 1991 split (Wikipedia)
- 227 codes activate only after full exhaustion: Per NANPA PL-603, central office codes in the 227 area code are only made available when all assignable central office codes in both 240 and 301 have been exhausted, meaning 227 numbers are issued as a last resort within the complex
FCC Regulatory History
Area code 301 has been the subject of five major regulatory actions since 1990, spanning NANPA planning letters and Maryland Public Service Commission decisions. These actions shaped the numbering plan for Maryland's western and suburban regions. Source: Wikipedia
| Year | Event | Docket | Regulatory Action & Impact |
|---|---|---|---|
| 1990 | 410 Split | NANPA IL 90-12-049 | Split of 301 NPA created area code 410 for Baltimore and Eastern Shore, effective October 6, 1991. Permissive dialing extended until November 1, 1992 |
| 1996 | 240 Overlay | NANPA IL 96-06-009 | Overlay of 301 NPA introduced area code 240 as general purpose overlay. Activated June 1, 1997. Mandatory 10-digit dialing from May 1, 1997 |
| 2001 | All-Services Overlay Framework | Maryland PSC Case No. 8853 | Maryland PSC approved all-services distributed overlay as relief method for 240/301 NPA. Established framework reserving area code 227 for future use |
| 2022 | 227 Overlay Approval | Maryland PSC | Approved NANPA petition to implement 227 area code overlay for 240/301 region. Estimated 240/301 exhaust in Q2 2023 (Maryland PSC) |
| 2022 | 227 Implementation Notice | NANPA PL-603 | Notified industry of 227 overlay implementation. Network preparation began September 14, 2022. In-service date June 14, 2023. 227 CO codes available only after 240/301 exhaustion |
County Coverage
Population-weighted county share based on aggregated ZCTA population (100% = total mapped population for area code 301).
| County | Population | Share |
|---|---|---|
| Montgomery, MD | 1,168,712 | 34.4% |
| Prince George's, MD | 1,082,938 | 31.9% |
| Frederick, MD | 336,420 | 9.9% |
| Charles, MD | 220,971 | 6.5% |
| Washington, MD | 173,549 | 5.1% |
| Howard, MD | 127,684 | 3.8% |
| St. Mary's, MD | 118,020 | 3.5% |
| Allegany, MD | 69,925 | 2.1% |
| Garrett, MD | 46,232 | 1.4% |
| Carroll, MD | 35,637 | 1.0% |
| Anne Arundel, MD | 7,512 | 0.2% |
| Calvert, MD | 7,512 | 0.2% |
Call Context
This area code covers multiple cities and communities across a broad region in Maryland. It is one of the original area codes established when the North American Numbering Plan was created in 1947.
Nearby Area Codes
Area codes geographically closest to 301.
Other Area Codes in Maryland
Area codes that also serve Maryland, linked for easy comparison.
Frequently Asked Questions
Common questions about area code 301 and how phone numbering works.
Phone numbers are assigned based on where the number was originally provisioned, not the caller's current location. Mobile phones retain their number when users move, and businesses may use numbers from regions where they don't have a physical presence. VoIP services can also provision numbers from virtually any area code.
Yes, mobile phones can have numbers from any area code in the region they were activated. Wireless carriers assign numbers from available pools regardless of phone type. When users change carriers or move to new areas, they typically keep their original number, which may have a different area code than their current location.
Start by looking up the area code on this site to understand its general geographic region. For the specific number, options include using your carrier's caller ID features or checking public directories. If you suspect fraud, you can report it to the FTC. To file a complaint about robocalls or spoofed numbers, visit the FCC Consumer Complaint Center. You can also register your number with the National Do Not Call Registry to reduce unwanted calls. Keep in mind that caller ID can display any name the caller chooses to set.
When an area's pool of available phone numbers runs low, regulators may introduce an "overlay" area code that covers the same geographic territory as the original. Both codes coexist, and new numbers are assigned from whichever code has availability. This area code shares its region with area code 227, area code 240. Learn more in our overlay vs split guide.
While Oakland is a prominent city in this area code's coverage, the code serves the broader surrounding region as well. Area codes are assigned geographically and typically cover multiple cities, towns, and communities beyond any single anchor city.
Yes, this is one of the original area codes established in 1947 when the North American Numbering Plan (NANP) was created. The initial set of area codes was designed to cover all of North America with a unified dialing system, and many of these original codes remain in use today, though some have been split or received overlays.