Quick hits from the archive
This page focuses on the four things that actually feel worth surfacing: active codes, referenced docs, overlay families, and split leaders.
The numbering plan started in 1947 because the Bell System needed a way to route long-distance calls more cleanly as the network grew. Area codes turned a big, operator-heavy system into something the switches could understand at scale.
In the original scheme, the middle digit was kept to 0 or 1 so area codes could be told apart from local exchange codes at a glance. That old rule is why the classic codes feel so patterned: 212, 303, 404, and the rest of the originals all fit that shape.
A blended score using event volume and unique source depth
Area code 809 was the original Caribbean numbering plan area code assigned around 1958, covering multiple Caribbean t...
Activity score 115 combines 55 events and 30 sources.
Area code for Alberta, Canada, assigned in 1947. Portions in the Northwest Territories were reassigned to 867 in 1997.
Activity score 95 combines 37 events and 29 sources.
Area code created in 1984 from a split of 212, covering Brooklyn, Queens, Staten Island, and Marble Hill in Manhattan.
Activity score 76 combines 34 events and 21 sources.
Area code 270 was created in 1999 as a split from 606, covering western Kentucky.
Activity score 74 combines 32 events and 21 sources.
Original area code for Atlanta, Georgia, covering the city and its suburbs inside Interstate 285.
Activity score 74 combines 32 events and 21 sources.
Original area code for all of New York City established in 1947, now covering Manhattan and the Bronx after splits an...
Activity score 73 combines 33 events and 20 sources.
Area code for the Seattle metropolitan area in Washington, originally assigned in 1947 and covering the western part...
Activity score 71 combines 29 events and 21 sources.
Original area code for southeastern Pennsylvania including Philadelphia, established in 1947.
Activity score 66 combines 26 events and 20 sources.
Source documents cited by the most events
PL-556 - Transition to 10-digit dialing (for 988 as 3-digit access to National Suicide Prevention Lifeline)
NANPA. 'PL-556: Transition to 10-digit dialing for 988.' January 8, 2021.
Area code 600
Wikipedia contributors. 'Area code 600.'
index.php?
Area codes 214, 469, 972, and 945. local PDF.
211 (telephone number)
Wikipedia, '211 (telephone number)', oldid 1347827975
Transition to 10-digit dialing (for 988 as 3-digit access to National Suicide Prevention Lifeline) – supersedes PL-544
PL-556
311 (telephone number)
311 (telephone number), local PDF extraction.
Florida's Area Code History
Sprint. 'Florida's Area Code History.'
Traffic Routing Guide
AT&T Traffic Routing Guide, 1975.
Grouped overlay families, sorted by size and activity
706 + 762
Northern and west central Georgia / Georgia
428 + 506
New Brunswick, Canada / New Brunswick
205 + 659
Alabama / Western and central Alabama
438 + 514
Montral Urban Area / Montréal Urban Area / Montreal Urban Area / Montreal, Quebec / Montreal
226 + 519
Southwestern Ontario, Canada / Southwestern Ontario
204 + 431
Manitoba / Manitoba, Canada
236 + 250 + 257 + 604 + 672 + 778
British Columbia
236 + 250 + 604 + 672 + 778
British Columbia, Canada
404 + 470 + 678 + 770 + 943
Atlanta metropolitan area, Georgia
281 + 346 + 621 + 713 + 832
Texas / Houston, Texas
368 + 403 + 587 + 780 + 825
Alberta, Canada
347 + 465 + 718 + 917 + 929
New York
Parent codes with the most split events behind them
809
612
Original Minnesota area code established in 1947, now covering Minneapolis and nearby suburbs after splits and boundary changes.
206
Area code for the Seattle metropolitan area in Washington, originally assigned in 1947 and covering the western part of the state until 1957.
213
404
Original area code for Atlanta, Georgia, covering the city and its suburbs inside Interstate 285.
904
Area code created in 1965 from a split of 305, covering northeastern Florida including Jacksonville and surrounding counties.
915
201
Original area code for all of northern and central New Jersey from 1947 until 1991, when it was split to create 908.