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.

Isabel, SD

NPA-NXX BLOCK Switch OCN LATA LIR Eff date Disc date
605-466 A EGBTSDXA964  1647 CHEYENNE RIVER SIOUX TRIBAL TEL. AUTHORITY 640      

Last updated: Thu, 05 Feb 2026 23:41:55 UTC

Sponsored by: FiberConX Communications Ltd.

Like this site? We accept donations via PayPal.