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.
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OCN: 4773 XO MARYLAND, LLC

NPA-NXX BLOCK Rate Centre Region Switch LATA LIR Eff date Disc date
443-578 A Cockeysville MD BLTMMDSNDS5  238      
443-578 0 Cockeysville MD BLTMMDSNDS5  238      
443-578 4 Cockeysville MD BLTMMDSNDS5  238      
443-578 5 Cockeysville MD BLTMMDSNDS5  238      

Last updated: Tue, 07 Oct 2025 16:47:53 UTC

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