| Overlay vs Split
Why splits are the best relief for large area codes
Why overlays are the best relief for small area codes
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 Chicago Illinois
The Chicago area has moved from one area code (312) in 1988 to nine area codes in 2022. The second area code went into service in 1989. Three more went into service in 1996. The first overlay went into service in 1998 with additional overlays in 2007, 2009 and 2022.
Northern Illinois (815) and central Illinois (217) have been overlaid and there are plans in place to overlay western Illinois (309) and southern Illinois (618).
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Illinois Area Code Map
Chicago Area Code History
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Indiana
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Indiana Area Code Map
Indiana Area Code History
Northern Indiana
(219, 260, 574)
Central Indiana
(317, 463, 765)
Southern Indiana
(812, 930)
Special Feature
1965 - GTE Richmond Central Office Fire(regular or frames)
Special Reports
1997 - Indiana's 317/765 Split
2002 - Indiana's 219/260/574 Split
2015 - Indiana's 812/930 Overlay
2016 - Indiana's 317/463 Overlay
Future Relief
2026? - Indiana 765/634? Relief
At least 20 years ...
- Indiana 219/943? Relief
- Indiana 260/834? Relief
- Indiana 574/665? Relief
Future NPA numbers 765, 574, 930 and 463 were 1) taken from an accidentally published working document, 2) absolutely not official, 3) subject to change and 100% accurate.
Future NPA numbers 634, 665, 834 and 943 are predicted.
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Michigan
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Michigan has moved from four area codes in 1961 to twelve in 2002. The last change in Michigan was the split of area code 269 from 616 in 2002. Michigan has only one overlay area code (947 overlaid 248 in 2002).
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Michigan Area Code History
Western Michigan
(231, 269, 616, 906)
Central Michigan
(517, 989)
Eastern Michigan
(248, 313, 586, 734, 810, 947)
Special Report
2002 - Michigan's 616/269 Split
Future Relief
2025 - Michigan 313/679? Overlay
2026 - Michigan 989 Relief
2027 - Michigan 734/278? Overlay
2030 - Michigan 231 Relief
2033 - Michigan 517 Relief
2034 - Michigan 269 Relief
2039 - Michigan 616 Relief
2048 - Michigan 586 Relief
At least 20 years ...
- Michigan 810 Relief
- Michigan 248/947 Relief
- Michigan 906 Relief
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Other NANP Sites
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Telecom Beyond
NANP Expansion
'Longer than 10 digit numbers'
My Plan for moving from 7D/10D to 8D/12D
Wireless Overview
Introducing Verizon Wireless
- America's First Mega-Carrier
Wireless Spectrum and Licencing
@TK.COM
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