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: CHCGILGM4MD

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
312-679 A Chicago Zone 01-Calumet IL 671J U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS 358   2026-03-31   
312-679 4 Chicago Zone 01-Calumet IL 671J U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS 358   2026-03-31   
312-679 5 Chicago Zone 01-Calumet IL 671J U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS 358   2026-03-31   

Last updated: Thu, 16 Jul 2026 02:21:55 UTC

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