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.

Switch: BLTMMDSNDS5

NPA-NXX BLOCK Rate Centre Region OCN LATA LIR Eff date Disc date
443-578 A Cockeysville MD 4773 XO MARYLAND, LLC 238      
443-578 0 Cockeysville MD 4773 XO MARYLAND, LLC 238      
443-578 4 Cockeysville MD 4773 XO MARYLAND, LLC 238      
443-578 5 Cockeysville MD 4773 XO MARYLAND, LLC 238      

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

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