Editing Overlay complex (section)

==Popularity==
Overlays were initially met with resistance, as they result in multiple area codes in the same geographic area, which requires ten-digit dialing. In many cases, such as [[area code 847|847]] in [[Chicago]]'s northwestern suburbs and [[area code 212|212]] in [[New York City]], an overlay was an additional disruption to a community that had already been subject to one or multiple code splits, encountering pushback from state regulators or consumer groups. However, overlay plans were eventually used much more widely in some areas than others. For example, much of [[List of Ohio area codes|Ohio]] has large overlay complexes, as has northern [[List of Georgia area codes|Georgia]] and the [[list of North Carolina area codes|North Carolina]] [[Piedmont (United States)|Piedmont]]. [[List of Connecticut area codes|Connecticut]], [[List of Illinois area codes|Illinois]], [[List of Oregon area codes|Oregon]], [[List of New Jersey area codes|New Jersey]], [[List of Massachusetts area codes|Massachusetts]], [[List of Maryland area codes|Maryland]], [[List of Pennsylvania area codes|Pennsylvania]], [[List of Texas area codes|Texas]], [[List of Virginia area codes|Virginia]] and, more recently, [[List of California area codes|California]] have also implemented many overlays.  No area code splits have been performed since 2007, when [[area code 575]] split off [[area code 505|505]] in [[New Mexico]], and no splits are proposed.

Telecommunications companies have increasingly favored overlays even in sparsely-populated rural areas in which ten-digit local numbers are unnecessary, as split plans force cellular providers to reprogram millions of client handsets. Customers also incur costs to publish new letterheads and to reprogram stored address book data on individual devices. Overlays have become more expedient as the proliferation of cell phones has accelerated area codes exhaustion. In most relief planning projects, overlays have become the sole option considered in the planning stage.<ref>{{cite web | url=https://www.nationalnanpa.com/reports/2021_NANPA_Annual_Report.pdf | title=NANPA 2021 Annual Report|date=March 2022|accessdate=2022-12-19|author=North American Numbering Plan Administrator}}</ref>

This is especially practiced for area codes that have been pushed back to the brink of exhaustion after being recently split, as carriers want to minimize additional customer inconveniences. For example, [[Maryland]] had been served solely by [[area code 301]] from the implementation of the area code system until 1990, when everything from [[Baltimore]] eastward was split off as [[area code 410]]. Within only five years, 410 was already on the brink of exhaustion due to Baltimore's rapid growth and the proliferation of cell phones, pagers, fax machines and dial-up Internet lines. However, the area's dominant telephone provider, Bell Atlantic (now part of [[Verizon]]) realized that a split would have forced residents of either Baltimore or the Eastern Shore to change their numbers for the second time in the 1990s. Accordingly, area code 443 was created as an overlay for all of the eastern portion of Maryland in 1996.

Overlay plans also favor [[ILEC|incumbent wireline carriers]] over new entrants, as the established firm already has large allocations of numbers in the more desirable existing code, and subscribers of new or growing [[competitive local exchange carrier|competing carriers]] are relegated to unfamiliar, new codes.

The first example of an area code overlaid on an entire U.S. jurisdiction was [[Puerto Rico]], with area code 939 added to the numbering plan area of area code 787, in 2001. Puerto Rico had just been split from [[area code 809]], the area code for much of the Caribbean, in 1996. A split was deemed unfeasible due to the island's extremely dense population and the lack of a suitable boundary for a split.{{citation needed|date=October 2022}} Additionally, a split would have forced half of Puerto Ricans to change telephone numbers for the second time in a decade.

The first instance of a ''statewide'' overlay was [[West Virginia]]'s [[area codes 304 and 681|area code 304]], in 2009. West Virginia had been served by 304 since the inception of the [[North American Numbering Plan]], but it was obvious by 2007 that the state needed a new area code. At first, state officials voted to split off northern West Virginia with area code 681 and to leave southern West Virginia in 304. However, lobbying by the telecommunications industry led the state to reverse the decision and turn 681 into an overlay. [[Idaho]] followed that precedent in 2017 by overlaying [[area codes 208 and 986|area code 208]] with 986.

Overlays gained popularity in the Canadian telephone network in the early 2000s, as they are a workaround for Canada's inefficient number allocation system. The proliferation of cellphones, fax machines, pagers, and dial-up Internet connections, particularly in larger markets, threatened central office code exhaustion in many areas. The area codes for four of the five largest Canadian markets ([[area code 416|416]] in [[Toronto]], [[area code 514|514]] in [[Montreal]], [[area code 604|604]] in [[Vancouver]], and [[area code 403|403]] in [[Calgary]]) were split in the 1990s.

Particularly severe allocation problems manifested themselves at the turn of the century in [[Metro Toronto]] and the [[Golden Horseshoe]], the center of Canada's largest local calling area. This area had been served by 416 since the institution of the area code system. Despite the Golden Horseshoe's explosive growth in the second half of the 20th century, numbers in the region were used up fairly quickly. As a result, the number allocation problem was not as severe in 416 as it was in the rest of Canada. Nevertheless, it was severe enough to force Toronto's suburban ring into [[area codes 905, 289, and 365|area code 905]] in 1993. While the Golden Horseshoe would have likely needed another area code due to its continued growth, it is very likely that the immediate need for relief would have been staved off had it been possible to reallocate numbers from the smaller rate centers in the region to Metro Toronto. Within two years of the 905 split, 416 was back on the verge of exhaustion. American cities such as New York City, Chicago, and [[Los Angeles]] had been split between two area codes, but that solution was quickly ruled out for Metro Toronto because of the area's extremely dense population and the lack of a suitable boundary for a split. It was ultimately decided to overlay 416 with area code 647 in 2001, two years after Metro Toronto was merged into the "megacity" of Toronto.

The successful implementation of 647 triggered the rapid adoption of overlays across Canada. By 2023, seven-digit dialing had been effectively eliminated nationwide in Canada (as well as in most of the United States), due to both overlays and other regulatory requirements. Overlays are now the preferred method of expansion in Canada, and no numbering plan areas have been split in the country since 1999.

[[British Columbia]] and the [[Prairie Provinces]] have followed Puerto Rico and West Virginia's lead with province-wide overlays. In those cases, a factor behind the decision was the desire to spare rural areas the expense and burden of changing their numbers.