The three-digit number, 717, serves as a geographic identifier for telephone communication within a specific region of the United States. It precedes the seven-digit local number and ensures calls are routed to the correct area. For example, a full phone number in this region would appear as 717-XXX-XXXX.
This numerical designator is essential for efficient telecommunications infrastructure. Its implementation allows for targeted call delivery and facilitates the expansion of phone services within the designated area. Historically, it was introduced as part of a nationwide system to manage the increasing demand for telephone lines.