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.

NPA: 312 [Rate centres in NPA 312] [Dial plan for NPA 312]

NXX: 255

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
312-255 A Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 0 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 1 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 2 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 3 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 4 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 5 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 6 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 7 Chicago Zone 01-Superior IL CHCGILCLXOX  516C AT&T CORP. 358      
312-255 8 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      
312-255 9 Chicago Zone 01-Superior IL CHCGILSUDS2  9329 ILLINOIS BELL TEL CO 358      

Last updated: Fri, 22 Mar 2024 03:02:44 UTC

Sponsored by: VoIP Much Phone Company

Like this site? We accept donations via PayPal.