Split

NANP · also called geographic split

The older relief method that divides an area code's geography, forcing part of the region onto a new area code.

A split is a form of area-code relief in which the geographic area of an existing NPA is divided, and one part is reassigned to a new area code. Everyone in the split-off region must change the area code of their telephone number.

Splits were the standard relief method into the late 1990s but have largely been replaced by overlays, which do not require anyone to renumber. Many current area codes trace their origin to a historical split.

Same goal — more numbers for a full area code — two methods. A split changes some people's numbers; an overlay changes no one's.

Common misconception.

"Split" and "overlay" are not interchangeable. A split reassigns part of the map to a new code and forces renumbering; an overlay layers a new code over the same map and forces only ten-digit dialing.