List of area code overlays
An area code overlay is a North American area code that is assigned to the same numbering plan area (NPA) as at least one other area code. Overlay codes are determined and regulated as part of the North American Numbering Plan to increase the number of available telephone numbers in a province, state or region.
The North American Numbering Plan Administration maintains the definitive list of overlay plans of area codes in the United States. The majority of overlay plans in North America have occurred since 1995. The process has been driven by fragmentation of numbering resources by a growing number of competitive local exchange carriers.
Active area code overlays
Pending and planned overlays
Various new area codes are planned or proposed. A few overlay implementations (557 MO, 564 WA, 689 FL, 975 MO) have been suspended, often because wasteful allocation of telephone numbers has been mitigated by number pooling or other conservation efforts.
- 332 is planned to overlay 212 and 646 in 2017.
- 387 is reserved as a future overlay for 416.
- 447 is planned for overlay of 217, with no precise time frame for integration.
- 464 is also reserved for 708, to be integrated once the original area code is exhausted.
- 470 will supplement the 678 overlay already present for 404 and 770 in Metro Atlanta. The new area code was announced in 2001, but will not be used until all assignable 678 NXX codes are exhausted.
- 564 planned for Washington area code 360 in 2017.
- 672 is proposed as a future overlay in British Columbia after 236 is exhausted.
- 679, planned to overlay 313 in Michigan.
- 680 is planned to overlay 315 in North Central NY. Anticipated start is 1Q 2017. 
- 742 is reserved as a future overlay for 905.
- 833 is proposed to overlay non-geographic toll-free codes 800 and 844 through 888 in mid-2017, largely due to failure of the Federal Communications Commission to enforce its regulations regarding hoarding, brokering or warehousing toll-free numbers.
- 835 is proposed to overlay 610 and 484. This plan has been suspended by the Pennsylvania Public Utilities Commission.
- 934 is proposed to overlay 631 in September 2016.
- 959 is to overlay Connecticut's 860. As with 475/203, it was proposed in 1999, but withdrawn.
- Haar, Dan and Vanessa Hua. "Regulators Have Area Code Plan". The Courant. August 18, 1999. Accessed October 28, 2005.
- NANPA : Number Resources - NPA (Area) Codes
- Madison, Linc. "LincMad's Area Code Locator Table". LincMad. September 29, 2005. Accessed October 28, 2005.
- "PSC Selects Overlay for New Area Code in Western Kentucky: Current numbers in area code 270 remain unchanged; decision means 10-digit dialing for local calls beginning in 2014". Retrieved December 17, 2012.
- "New 669 Area Code Joins South Bay 408 Region Saturday". KPIX-TV.
- NANPA PL-269
- "New area code coming to western Washington" (Press release). Washington Utilities and Transportation Commission. May 19, 2016. Retrieved May 19, 2016.
- "NANPA : Number Resources - NPA (Area) Codes".
- "New 680 Area Code Officially Announced for Central New York". WKTV.
- David B. Caruso (2011-04-20). "Hot numbers when you least expect them". Associated Press. Retrieved 2013-11-07.
- Area Codes in Southeast Pennsylvania