640 Area Code – Trenton, New Jersey: Location, Time Zone & History

Unlike most area codes, 640 was never carved out of a geographic split -- it exists entirely layered on top of area code 609, covering the same central and southern New Jersey territory that includes Trenton, Princeton, Atlantic City, and Long Beach Island. Regulators chose this all-services overlay approach specifically to avoid forcing existing 609 customers to change their numbers.

The rollout followed a clear timeline. A 2014 forecast projected that the 609 number pool would run out by roughly the second quarter of 2017, prompting the overlay decision. Permissive dialing with the new code began January 20, 2018, ten-digit dialing became mandatory that August 18, and 640 was put into service on September 17, 2018.

Because 640 and 609 draw from the same pool, a new phone line in Trenton, Princeton, or Atlantic City is about as likely to receive one code as the other, and both carry the same state-government and political identity tied to New Jersey's capital. The shared territory also includes Ewing and Hamilton, with economic anchors in casino gaming and tourism around Atlantic City, higher education and pharmaceutical research at Princeton, and state government functions centered in Trenton.