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: 857 [Rate centres in NPA 857] [Dial plan for NPA 857]

NXX: 433

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
857-433 A Boston MA BSTRMAQNAMD  0051 SHELCOMM 128   2026-06-26   

Last updated: Thu, 16 Jul 2026 02:21:55 UTC

Sponsored by: VoIP Much Phone Company

Like this site? We accept donations via PayPal.