The area code 640 is located in Allentown, New Jersey.
Area code 640 serves Allentown, New Jersey as part of an overlay with long-standing area code 609 in central and southern New Jersey. This overlay covers parts of Monmouth, Mercer, Burlington, Atlantic, Cape May, and Ocean counties, linking small towns like Allentown with regional hubs and coastal communities. In Allentown—a historic borough in Monmouth County near I‑195—640 phone numbers connect residents and businesses to nearby Trenton and the Jersey Shore while keeping local calling simple with ten-digit dialing. Existing 609 numbers did not change when 640 launched, so both area codes work side by side across the same footprint.
Where area code 640/609 is commonly found:
Introduced in 2018, area code 640 was added to meet growing demand for phone numbers in the 609 region, which dates back to 1958 and later split to create 856 in 1999. With the 640 overlay, 10-digit dialing is required for local calls, but calling areas and rates remain the same. Fun fact: 640 is the first overlay for the historic 609 territory, home to major landmarks like Princeton University and the Atlantic City casino district. “NANPA identifies 640 as the overlay for 609” (Source: North American Numbering Plan Administration), ensuring Allentown and neighboring communities have plenty of number capacity for new phones, businesses, and services.