When the North American Numbering Plan was established by AT&T in October 1947, Nassau and Suffolk counties, the lower Hudson Valley, and some areas adjacent were assigned area code 914. At the time, this area was largely coextensive with the New York state portion of the New York metropolitan area. In 1951, Nassau and Suffolk were designated as a separate numbering plan area with area code 516.
Despite Long Island's growth in both population and telephone service during the second half of the 20th century, this configuration remained for five decades. By the late 1990s, the proliferation of pagers and cell phones required further division to provide more telephone numbers for Long Island. On November 1, 1999, Suffolk was separated as a new numbering plan area with area code 631, while Nassau retained 516. Permissive dialing of 516 across Long Island continued until spring 2000.
Area code 516 has telephone numbers assigned for the central office code 988. 988 has been designated nationwide as a dialing code for the National Suicide Prevention Lifeline, which creates a conflict for exchanges that permit seven-digit dialing. This area code is therefore scheduled to transition to ten-digit dialing, mandatory after October 24, 2021.
A 2018 NANP analysis of numbering resources projects exhaustion of NPA 516 during the fourth quarter of 2023, but the results have since varied between 2024 and 2025.
- 1947 Original Area Code Assignments, Linc Madison, a.k.a. LincMad Consulting
- Rather, John (October 31, 1999). "Suffolk County Gears Up for 631 Area Code". The New York Times.
- "Transition to 10-digit dialing (for 988 as 3-digit access to National Suicide Prevention Hotline)" (PDF). North American Numbering Plan Administrator. January 8, 2021. Retrieved March 9, 2021.
- 2020 October NANPA Exhaust Projections
- NANPA area code map of New York
- List of exchanges from AreaCodeDownload.com, 516 Area Code
- Interactive Map of Area Code 516
|North: 914, 203/475|
|West: 347/718/929/917||area code 516||East: 631/934|
|South: Atlantic Ocean|