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.

OCN: 907D INTERSTATE TELECOMMUNICATIONS COOPERATIVE, INC.

NPA-NXX BLOCK Rate Centre Region Switch LATA LIR Eff date Disc date
605-405 9 Arlington SD WTTWSDCO0MD  640   2021-09-12   
605-438 A Milbank SD WTTWSDCO0MD  640      
605-621 A Madison SD WTTWSDCO0MD  640      
605-621 9 Madison SD WTTWSDCO0MD  640   2023-05-04   
605-954 9 Watertown SD WTTWSDCO0MD  640   2019-09-23   

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

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