─────── § 04. NPA RECORD · 312 · FOLIO 0114 OF 0801 ──────────────
312
United States NPA Record
Area code for downtown Chicago, Illinois, one of the original North American area codes established in 1947.
Area code for downtown Chicago, Illinois, one of the original North American area codes established in 1947.
IN SERVICEFirst record · 1988
§ 04.05Event Summary
split · 5other · 3mandatory dialing · 2permissive dialing · 1relief planned · 1
§ 04.06
Documentary Record · 15 events
CHRONOLOGICAL ORDER
1988-04-08
other
NANP - SPLIT OF THE 312 NUMBERING PLAN AREA
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1989-01-01
split
NPA 708 split from 312
Area code 708 was created in 1989 as a geographic split from area code 312 to serve the suburbs of Chicago, Illinois, leaving 312 for the city proper.
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1989-04-21
other
312 NUMBERING PLAN AREA (NPA) CODE SPLIT IN ILLINOIS
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1989-11-11
split
NPA 708 split from 312
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1996-02-29
other
NANP-Split of 312 (Illinois) Numbering Plan Area (NPA)
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1996-10-01
split
NPA 773 split from 312
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1996-10-11
split
NPA 773 split from 312 for outer Chicago
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1996-10-12
split
NPA 773 split from 312 for Chicago's outer areas
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1996-10-12
permissive dialing
Permissive dialing period begins for 773 and 312
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1997-01-11
mandatory dialing
Mandatory dialing of 773 and 312 begins
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2007-08-10
relief planned
Overlay planned for 312 and 773 with 872
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2009-06-15
NPA 872 overlay on 312 announced
NPA 872 to Overlay NPA 312 and 773 (Illinois)
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2009-08-10
NPA 872 overlay on 312 announced
NPA 872 to Overlay NPA 312 and 773 (Illinois)
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2009-11-07
NPA 872 overlay activated for 312 and 773
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2009-11-07
mandatory dialing
Mandatory 11-digit dialing for 312, 773, and 872
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