Telecom Rate Center Maps
Verizon defines a telecom rate center as:
The specific geographic point and corresponding geographic area that are associated with one or more particular NPA/NXX codes that have been assigned to a local exchange carrier for its provision of exchange services. The geographic point is identified by a specific coordinate that is used to calculate distance-sensitive end user traffic to/from the particular NPA/NXX associated with the specific Rate Center.
Maponics no longer provides rate center maps but does provide NPANXX Data.