Area Code Atlas

Geographic Split of 516 (New York) Numbering Plan Area (NPA); addition of 631 NPA

NPA 631 split from 516 for Suffolk County

Area code 631 was created on November 1, 1999, as a geographic split from 516 to serve Suffolk County, New York, due to increased demand for telephone numbers including cellular services.

Mandatory use of area code 631 in Suffolk County

Permissive dialing for numbers terminating in the 631 area ended on April 1, 2000. After this date, callers were required to use area code 631 for calls within Suffolk County, ending the permissive period during which both 516 and 631 could be used.

Permissive dialing period for 631 begins

Permissive dialing began on April 1, 2000, allowing both area codes 516 and 631 to be used to dial numbers in the new 631 area, facilitating transition after the split.

New central office codes activated in 631

New central office codes in area code 631 could be activated starting May 8, 2000, expanding numbering capacity in Suffolk County following the split from 516.

Extended Permissive Dialing Ends for 516/631 NPAs (New York)

NPA 934 overlay on 631 announced

NPA 934 to Overlay NPA 631 (New York)

Mandatory ten-digit dialing for NPAs 631 and 934

Ten-digit dialing became mandatory for both area codes 631 and 934 in Suffolk County on June 18, 2016, coinciding with the introduction of the 934 overlay.

NPA 934 overlays 631 in Suffolk County

Area code 934 was introduced as an overlay to area code 631 on July 16, 2016, in response to the depletion of available central office codes in the region. This was the first overlay implemented outside New York City in the state.

Overlay area code 934 assigned to 631

Area code 934 was assigned on July 16, 2016, as an overlay to area code 631 in Suffolk County to address the nearing depletion of central office codes, marking the first overlay in New York State outside New York City.