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: 231 [Rate centres in NPA 231] [Dial plan for NPA 231]

NXX: 243

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
231-243 A Alanson MI   817J INTERACTIVE SERVICES NETWORK, INC. 348      

Last updated: Thu, 20 Nov 2025 13:34:34 UTC

Sponsored by: VoIP.ms

Like this site? We accept donations via PayPal.