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: CHCGILIDDS2

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
312-329 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-379 1 Chicago Zone 01-Calumet IL 9329 ILLINOIS BELL TEL CO 358   2002-06-03   
312-410 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-467 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-494 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-644 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-645 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 0 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 1 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 3 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 4 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 7 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 8 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-661 9 Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      
312-670 A Chicago Zone 01-Illinois Dearborn IL 9329 ILLINOIS BELL TEL CO 358      

Last updated: Sat, 04 Jul 2026 13:07:56 UTC

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