“Permissive” refers to the date at which it became possible to use either the old or the new area code. However, for overlays, this column shows the date on which 10D or 1+10D dialing became mandatory.

“Mandatory” refers to the date at which it became necessary to use the new area code. If you dial the old area code after the mandatory date, you will reach an error recording, or worse, a wrong number. However, for overlays, this column shows the date on which numbers in the new overlay code became dialable.

After substantial public resistance to the idea of area code overlays, primarily because of the requirement to dial the area code on all calls, the tide has turned. The last area code split in the United States was in 2007–2008; the last split in Canada was in 1999. Indeed, Canada has officially announced that, barring exceptional circumstances, all future new area codes in Canada will be overlays. There are a few cases in the United States where a split might still be considered, but it is likely that most if not all new area codes will also be overlays.

Area code 456 was assigned for inbound international calls, particularly 56K ISDN data calls, where it was essential to connect the inbound call to a particular carrier’s network. However, by 2017 the need for such special routing had evaporated, so the 456 NPA has been discontinued. In 2023, 456 will be made available for assignment as a general-purpose NPA.

The Caribbean island of St. Martin is divided between France and the Netherlands. The Dutch side, known as Sint Maarten, has joined the North American Numbering Plan as area code 721; Sint Maarten has also been assigned ISO country code SX, and the corresponding .sx Internet domain is now in use. The change was originally scheduled for 2010, but was postponed until 2011‑09‑30 (permissive), 2012‑09‑30 (mandatory). You now must use +1 721; from North America, dial 1‑721. All current 7-digit numbers in Sint Maarten begin with ‘5’, but new numbering ranges will be added in the future. The French side continues to use +590, or 011‑590 from North America (including calls from Sint Maarten to French Saint-Martin). (The French side now has the ISO country code MF, but .mf is not used for the Internet. Use either .gp (Guadeloupe) or .fr (France) for French St.‑Martin.)

nl: Het Caribische eiland Sint Maarten is verdeeld tussen Frankrijk en Nederland. Het Nederlandse deel heeft zich aangesloten bij de Noord-Amerikaanse Nummering Plan (+1) zoals het netnummer 721. De verandering was oorspronkelijk gepland voor 2010, maar werd uitgesteld. Permissieve bellen eindigde 2012‑09‑30, en de nieuwe nummers zijn nu verplicht. Alle huidige 7-cijferige nummers in Sint Maarten beginnen met ‘5’, maar nieuwe nummering reeksen kunnen worden toegevoegd. Gebruikt u de internationale landcode +1 721; uit Noord-Amerika, kies 1–721. Het Franse deel zal blijven +590 te gebruiken, of 011–590 uit Noord-Amerika. De andere Nederlandse eilanden in het Caribisch gebied niet veranderd. Sint Maarten is toegewezen ISO-landcode SX en de .sx Internet-domein.

fr: L’île antillaise de Saint-Martin est divisée entre la France et les Pays-Bas. La partie néerlandaise, Sint Maarten, a rejoint le Plan de Numérotation Nord-américain (+1) avec l’indicatif régional 721 et le domaine de l’Internet .sx (actuellement en vigueur). Pourtant, la transition a été remise. Composition facultative (composer +599 ou +1 721) a commencé le 2011‑09‑30; à partir du 2012‑09‑30, le +1 721 est obligatoire. Tous les numéros actuels à 7 chiffres à Sint Maarten commencent par ‘5’, mais d’autres numéros pourraient être ajoutés. Pendant la période permissive, on pouvait utiliser l’indicatif de pays +599 ou l’indicatif nord-américain +1 721; en Amérique du Nord, composer le 011–599 ou le 1–721. Maintenant il faut utiliser seulement +1 721. La partie française continuera d’utiliser +590, ou 011–590 d’Amérique du Nord.

Area code 512 in central Texas was planned for a concentrated overlay in 2001, with Austin, Georgetown, and San Marcos in the 512 & 737 overlay, while outlying communities including Lampasas, Lockhart, Dripping Springs, Taylor, Bastrop, and Jarrell would have remained only in 512. However, the plan was shelved when number conservation efforts significantly extended the life of 512. The overlay was finally resurrected in 2012; it took effect 2013‑07‑01 as a general overlay of 737 on the entirety of 512.

Area code 216 (Cleveland, Ohio) split in 1996, with Akron, Canton, and Youngstown moving to the new area code 330. A second split took place on 1997‑08‑16, with the lakefront outside of Cleveland moving to area code 440. At the same time, however, several communities between Cleveland and Akron switched from 216 to 330. The affected exchanges are Hudson, Twinsburg, Northfield, Aurora, Peninsula, and Richfield. There was a similar realignment of the 513/937 boundary between Cincinnati and Dayton, in mid-2001 in anticipation of the 513 & 283 overlay. The Franklin exchange realigned from 513 to 937 rather than becoming part of the overlay. (The 513 & 283 overlay is now expected to happen some time around 2019.)

The Dallas and Houston metropolitan areas in Texas had geographic splits in 1996. Both areas again ran out of numbers. In December 1998 and January 1999, the most recent split boundaries were officially “erased”; an additional area code was overlaid in each city in 1999, and a fourth area code was added in the Houston area in 2014.

State authorities in Pennsylvania cancelled the scheduled overlay of area code 412 (western Pennsylvania, including Pittsburgh) that was to take effect on 1997‑05‑01. The reason for the reconsideration is that the original plan was to continue to allow local calls within the same area code to be dialed with only the 7-digit number, but FCC regulations require that the area code be dialed on all calls in an overlay area. Regulators decided on a conventional split, with Pittsburgh and some immediate suburbs retaining 412 and the rest of southwest Pennsylvania changing to 724. [back to table] However, in August 2001, the 412 and 724 area codes were reunited under the single 878 overlay, with 10-digit local dialing on all calls. However, as of 2020‑04‑09, only 56 prefixes (out of nearly 800) in area code 878 are in use, with 13 more in the planning stages, suggesting that the 2001 overlay was more than a little premature.

The Commonwealth of the Northern Mariana Islands (CNMI) and Guam are U.S. territories in the Pacific Ocean. Each had a standard international country code assigned. Beginning on 1997‑07‑01, and continuing permissively for one year, it was possible to dial these islands using either the old country code or a North American area code. From 1998‑07‑01, only the new North American area code may be used. From within North America, these points must be dialed “1+” instead of “011+”; from outside North America, the country code “1” must be used. (Indeed, country code +670 has now been assigned for TL Timor-Leste/East Timor.) American Samoa changed from +684 to +1 684 in 2004, and there has been speculation that other Pacific islands might also join the NANP, but there has been no formal proposal to do so. However, on 2011‑09‑30, the Dutch Caribbean island of Sint Maarten, formerly in country code +599, joined the NANP as area code 721; the French side of the same island remains in country code +590, and other islands in the Caribbean Netherlands (BES islands) and Curaçao remain in country code +599. Aruba remains in country code +297.

Officials in Massachusetts, citing the rapidly diminishing supply of numbers in the greater Boston area, advanced the timetable for the splits of area codes 617 and 508, and then pushed back the mandatory date on two further occasions. The final dates are shown above. Note that the final mandatory date coincides with the originally planned permissive date! The state legislature also imprudently played politics with the split boundaries for the 617/781 split. First the suburbs of Watertown and Belmont were reinstated into 617 via a rider on an unrelated piece of legislation. Then ten other suburbs whined “Us, too!” to which the legislature caved in. The acting governor vetoed this lunacy, and, in fairness to the second set of suburbs, introduced a bill to return Watertown and Belmont to area code 781 as originally slated. That bill died in the state legislature; the splits have gone mandatory, with no indication that Watertown or Belmont will be reinstated into 781 where they belong. Had all twelve of these suburbs retained the 617 area code, another split of 617 would have been required in less than one year! As it stands, Massachusetts has already announced the next round of new area codes for 617 and 508 and their offspring, with overlays coming in April 2001. Each of the four area codes will receive a separate overlay code: 617 & 857, 781 & 339, 508 & 774, and 978 & 351. The rules for dialing numbers in the overlays are not yet clear, since Massachusetts has a confusing mish-mash of rules. In some cases, 1+ is required on a call that carries no toll, and in other cases 1+ is not required on a call that is charged at higher rates than calls within the same exchange.

For details of the multiple splits of the old area code 809 in the Caribbean, see the separate page.

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