Texas The blue area is assigned area codes 301, 240, and 227; the red area is area codes 410, 443 and 667 The state of Maryland is served by the following area codes: Area codes Numbering plan area 227240301 western Maryland, including its suburbs of Washington, D.C. 410443667 eastern Maryland including Baltimore and Annapolis Lists of area codes in the North American Numbering PlanUnited States Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware District of Columbia Florida Georgia Hawaii Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah U.S. Government Vermont Virginia Washington West Virginia Wisconsin Wyoming American Samoa Commonwealth of the Northern Marianas Guam U.S. Virgin Islands Other Canada Caribbean Former Belize Costa Rica Cuba El Salvador Guatemala Haiti Honduras Mexico Nicaragua Panama