The first three digits of a ten-digit phone number are known as an area code. These numbers represent a specific geographic area in North America. Once exhausted, a new area code is required.
Exhaustion is due to a number of different factors.
Another factor is the method by which numbers are assigned to local phone companies. Phone numbers are assigned to local phone companies in blocks of 10,000. Presently, if a local company does not have a need for that many numbers, the numbers go unused. Additional codes will continue to be created in response to these factors. The PUCO then creates a planning team to develop solutions for that affected area code based in part upon public input.