301 Area Code
The 301 area code is used by SOME cities and towns in these Counties / Independent Cities:
| Allegany County | Cities & Towns | ZIP Codes | Features |
| Anne Arundel County | Cities & Towns | ZIP Codes | Features |
| Calvert County | Cities & Towns | ZIP Codes | Features |
| Charles County | Cities & Towns | ZIP Codes | Features |
| Frederick County | Cities & Towns | ZIP Codes | Features |
| Garrett County | Cities & Towns | ZIP Codes | Features |
| Howard County | Cities & Towns | ZIP Codes | Features |
| Montgomery County | Cities & Towns | ZIP Codes | Features |
| Prince Georges County | Cities & Towns | ZIP Codes | Features |
| Saint Marys County | Cities & Towns | ZIP Codes | Features |
| Washington County | Cities & Towns | ZIP Codes | Features |
