Find Maryland Phone Codes

Dialing Within Maryland

Every Maryland number is 10 digits, and you dial all 10 every time, even to the house next door. That has been true since 1997, when the first overlay area codes arrived. Long distance adds a 1 in front. An operator-assisted call starts with 0 instead. Nothing about the length of the number changes, only what goes ahead of it.

The table sorts out which phone code goes where, by the kind of call you are placing.

Seven-digit dialing is gone for good here. A call placed without the area code simply fails, which surprises people who moved from a state with a single code.

Three-Digit Service Phone Codes in Maryland

The three-digit codes are the ones most people use without thinking. Each one is set aside nationally, but what answers on the other end is often local. In Maryland, 211 reaches a statewide service, 511 reaches the state highway system, and 311 only works if your county happens to run one.

511 is the one Maryland drivers underuse. It carries traffic, incident, and work zone information from the state, and the same data is published online.

Maryland 511 and CHART is the web version of what the phone code reads out.

Cameras, incidents, and travel times are all on the map, which is worth checking before a drive rather than during one.

Maryland Relay and the 711 Phone Code

711 deserves its own mention because it shows up on nearly every state and county contact page in Maryland, usually as a line of small print. Dialing it connects a caller to Maryland Relay, where an operator bridges a conversation between a standard voice call and a text or assistive device. Several agencies also publish 800-735-2258 as a direct relay number.

Maryland Relay explains how a call is placed and what the operator does.

The state directory of employees also carries a separate TTY listing, which is easy to miss under the main search fields.

Star Phone Codes on Maryland Lines

Star codes, known formally as vertical service codes, tell your own carrier to do something with the next call. They are strongest on traditional landlines. Mobile phones and internet phone services support some of them and ignore others, so check with your provider before relying on one. The list below is the standard national set that NANPA publishes.

*57 is the one worth remembering after a threatening call. It records the trace with the carrier rather than showing you anything, so it works alongside a police report instead of replacing one.

The official list of these phone codes is maintained by NANPA.

Carrier support varies, so the reference tells you what a code means rather than guaranteeing it will work on your line.

Area Phone Codes Serving Maryland

Area codes are phone codes too, and Maryland has six of them in two groups. They matter here mainly because you dial them on every call, including local ones. Which code a new number gets depends only on which group covers that part of the state.

• 301 - the original Maryland code, in use since 1947
• 240 - overlay on 301 since 1997
• 227 - overlay on 240 and 301 since 2023
• 410 - split from 301 in 1991
• 443 - overlay on 410 since 1997
• 667 - overlay on 410 and 443 since 2012

Which counties fall under each group, and why an overlay forces 10-digit dialing, is covered on the Maryland phone area codes page.

Toll-Free Phone Codes

Toll-free prefixes look like area codes but work nothing like them. They have no geography at all. The charge lands on the business being called instead of the caller, which is why state agencies and utilities publish them alongside a local number. Each prefix was opened as the one before it filled up.

The separate pools trip people up. Dialing 888 instead of 800 on a number you half remember does not reach the same business. It reaches whoever holds that number, which may be nobody or may be a scam operation that bought it on purpose.

Premium-rate services in the 900 range are a different thing again. Those charge the caller by the minute and have nothing to do with Maryland geographic codes.

Country Code and International Phone Codes

Maryland sits inside the North American Numbering Plan, so the country code for every number in the state is +1. You almost never dial it at home. It matters when someone abroad calls you, or when you call out.

1. Calling another country from a Maryland landline: dial 011, then the country code, then the number.
2. Calling another country from a mobile in Maryland: press and hold 0 for the plus sign, then the country code, then the number.
3. Calling Maryland from abroad: dial that country's exit code, then 1, then the full 10-digit Maryland number.

The plus sign is the safer habit on a mobile, since it works from any country without knowing the local exit code.

Local Exchange Phone Codes in Maryland

The three digits after the area code are the exchange, or NXX. Once upon a time they pointed at a physical building full of switching equipment. Today they still map to a rate center, which is the billing area the network uses, and Maryland has dozens of them: Baltimore, Towson, Annapolis, Frederick, Gaithersburg, Catonsville, Salisbury, Columbia, Hagerstown, Waldorf, Cumberland and more.

These phone codes still carry a hint of origin. A prefix assigned to a carrier in the Gaithersburg rate center did start life there. But number portability means the customer holding that number today may have moved it to a mobile carrier, an internet service, or another state entirely. Treat the exchange as history rather than as a current address.

Spam Labels and Caller ID Authentication

When a Maryland phone shows "Likely Spam" or "Spam Risk," that label did not come from any phone code in the number. It comes from the carrier. STIR/SHAKEN is the authentication system carriers use to check whether a call is really allowed to use the caller ID it is showing. It does not vouch for the person calling. It only confirms the number was not obviously faked.

Labels are also fed by call analytics, user reports, and patterns that look automated. That is why a legitimate small business or a doctor's office sometimes gets flagged by mistake. If your own number is being mislabeled, the carrier is the place to start, and the FCC takes complaints about it too.

The FCC proposed further changes in December 2025 that would add verified caller names and mark calls that originate outside the country.

Phone Code Definitions

A handful of terms come up whenever phone codes are discussed, and most of them are shorter than they sound.

NPA

Numbering Plan Area, the formal name for a three-digit area code.

NXX

The central office code, meaning the three digits between the area code and the last four.

N11

The set of three-digit service codes reserved nationally, such as the ones listed above.

Vertical service code

A star code that changes how your line handles the next call.

Toll-free prefix

A code that shifts the cost of the call to the party being called.

NANP

The North American Numbering Plan, the +1 region covering the United States, Canada, and 23 other territories.

Looking Up a Maryland Phone Code

Any phone code can be checked against a public source. NANPA handles the numbering side, from area codes down to exchange assignments. The FCC handles the policy side and publishes plain-language guides on the three-digit codes and on why 10-digit dialing exists. For anything specific to this state, including landline service questions, the Public Service Commission is the right office.