667 Area Code – Baltimore, Maryland: Location, Time Zone & History

Baltimore's telephone numbering has been reshaped twice by growth since Maryland first split area code 410 off from 301 on October 6, 1991 to cover the Baltimore metropolitan area and the Eastern Shore. Within five years, the supply of 410 numbers was already running low, so 443 was added as an overlay on June 1, 1997. Continued growth, especially in cell phone numbers, pushed the combined pool toward exhaustion again, and area code 667 entered service on March 24, 2012 as a second overlay — introduced specifically so existing 410 and 443 customers would not have to change their numbers. Regulators did not expect a fourth code to be needed until roughly 2030.

The 410/443/667 numbering plan area covers Baltimore itself along with Annapolis, Columbia, Ellicott City, Glen Burnie, and Towson. Its economy is anchored by healthcare and biomedical research tied to Johns Hopkins, shipping and logistics through the Port of Baltimore, defense and aerospace work at Aberdeen Proving Ground, finance and insurance, and tourism centered on the Inner Harbor.

Culturally, the region carries deep historical weight: Fort McHenry, in Baltimore Harbor, is where the Star-Spangled Banner was written, and further out on the Eastern Shore, the Chesapeake Bay blue crab industry remains central to local identity.