Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
  • Effective date searches are available only for US area codes. Our sources for non-US NPA-NXX data do not provide this information.
  • If you want to search an entire area code regardless of activity, leave both the next and past days fields set to zero.

Switch: CHCGILCADS0

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
312-326 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-328 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-528 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-567 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-570 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-674 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-791 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-808 A Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358      
312-945 A Chicago Zone 01-Wabash IL 9329 ILLINOIS BELL TEL CO 358      

Last updated: Thu, 01 Jan 2026 03:59:49 UTC

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