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Area Code 312: Comprehensive Guide to Chicago's Downtown Code

Info: Area code 312 is a key telephone area code in the North American Numbering Plan (NANP) for Chicago, specifically covering downtown and the Chicago Loop. It operates alongside area codes 773 and 872 in an overlay complex.

Key Technical Specifications

  • NPA Code: 312
  • Type: Overlay
  • Implementation Date: 1947
  • State: Illinois

Geographic Coverage

Area code 312 is designated for the downtown region of Chicago, Illinois, including the Chicago Loop. Despite being one of the smallest area codes by geographic size, it serves a densely populated urban area.

Major Cities

  • West Chicago, Illinois: Coordinates (41.88475, -88.20396)

Numbering and Utilization Statistics

  • Total Numbers Available: Approximately 7.92 million
  • Utilization Rate: High
  • Exhaust Projection: Managed with overlay codes 773 and 872

Network Infrastructure

Major Carriers

  • AT&T
  • Verizon
  • T-Mobile
  • Comcast

Available Services

  • Landline
  • Wireless
  • VoIP

Regulatory and Compliance Details

  • Regulatory Body: Illinois Commerce Commission (ICC)
  • Dialing Requirements: Ten-digit dialing required for all local calls within the overlay complex
  • Compliance: Adheres to North American Numbering Plan Administration (NANPA) guidelines

Historical Milestones

  • 1947: Area code 312 was among the original 86 numbering plan areas created for the NANP.
  • 1989: Suburbs were assigned area code 708, concentrating 312 to Chicago.
  • 1996: Area code 773 was split from 312, making it an enclave area code.
  • 2009: Area code 872 was overlaid on 312 and 773, necessitating ten-digit dialing.

Conclusion

Area code 312 is integral to Chicago's telecommunications, particularly in its downtown area. Its limited geographic scope and high usage rates demand strategic management and the use of overlay codes to maintain number availability. The regulatory framework and historical developments underscore the evolving nature of area code management in densely populated urban settings.

For further reading, visit the official Wikipedia page on Area Code 312.