Description: U.S. Telephone Area Code Boundaries provides the telephone area code boundaries of the United States for use in telecommunications analysis. U.S. Telephone Area Code Boundaries represents the telephone area code boundaries for the United States. They are also known as Numbering Plan Areas (NPA). The Numbering Plan Areas reflect current and accurate boundary changes both where new NPAs split from existing NPAs and where new NPAs overlay existing NPAs.<br /><br />When an NPA is split, the geographic area covered by the area code is divided geographically, with one portion retaining the previous area code and the other switching to the new area code. When a new NPA is added as an overlay, the area code remains unaffected. Instead, all or part of the land covered by the area code is now covered by the previous and new area codes.