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: 406 [Rate centres in NPA 406] [Dial plan for NPA 406]

NXX: 878

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
406-878 A Great Falls MT MSSLMTXC7MD  732J NUSO, LLC 648      
406-878 2 Great Falls MT MSSLMTXC7MD  732J NUSO, LLC 648   2023-03-30   
406-878 8 Great Falls MT   145J TERRA NOVA TELECOM INC. 648   2025-10-09   

Last updated: Thu, 16 Oct 2025 03:04:18 UTC

Sponsored by: ISP Telecom

Like this site? We accept donations via PayPal.