The Maine Public Utilities Commission opened an investigation Tuesday into the dwindling numbers available in the 207 area code, the sole area code used in Maine.

The probe will focus specifically on the number-forecasting practices of telecommunications provider Verizon, which the PUC said is predicting a faster exhaustion of phone numbers in Maine than is supported by historical data.

Tuesday’s action follows an initial assessment of the 207 area code announced last year. After three-quarters of a century, Maine no longer has access to most of the 8 million phone numbers in its 207 area code. Based on expected demand, Maine’s area code is “exhausted,” meaning it could run out of usable numbers by late 2024.

Twenty-five states have added multiple area codes, according to CTIA, the national association that represents wireless carriers. Maine should join that list, the carriers have said. In today’s mobile society, a growing number of people have phones with out-of-state area codes.

Based on a review of phone number resource requests from Verizon from January 2020 through June 18, 2021, the PUC said it has reason to question the company’s forecasting process for numbering resources.

“Maine’s 207 area code is dwindling rapidly,” PUC Chairman Philip L. Bartlett said in a statement. “And while there may be a time when Maine has to accept a new area code, it would be a shame for one company’s practices to hasten that time if it has no actual need for the numbers.”

Bartlett said that based on data received by the commission, “Verizon may be using unrealistic forecasting goals, unnecessarily tying up available phone numbers.”

The investigation directs Verizon to provide the PUC with detailed information including available phone numbers and percentage utilization in all rate centers and a detailed explanation of why forecasted growth is greater than historic growth.

The PUC also has petitioned the Federal Communications Commission to direct the North American Numbering Plan Administrator to report on the technical, operational and cost requirements to implement number optimization measures in the 207 area code. The commission also has worked with carriers on mitigation strategies, which have resulted in the return of more than 600,000 numbers to the numbering pool from unused or slightly used blocks.

Verizon did not respond to a request for an interview on the issue Tuesday. The company has until Aug. 17 to file a formal response in the case.

Area codes came into use in North America in the 1940s and are technically called Number Plan Area, or NPA, codes. The Bell System, led by the former Bell Telephone Co., initially created 86 area codes as part of setting up a long-distance, direct dialing system, according to allareacodes.com, an online resource for the North American Numbering Plan. The second digit was always a zero if it covered an entire state or Canadian province, such as 207 for Maine. And it was a one if it covered just a region, such as 617 for Boston.

The next set of three digits is the central office or exchange code. Each exchange code contains roughly 10,000 usable telephone numbers, broken into 10 “blocks” of 1,000 numbers each.

The final four digits are the subscriber or line number. Each block of 1,000 is used for the last four digits of 1,000 telephone numbers.
North America’s telephone number supply is controlled by an administering agency and contractor that maintain a pool of unused area codes and exchanges, and blocks of line numbers. But in three years, based on projections, there won’t be enough numbers in the 207 pool to handle the growing demand for mobile and other wireless devices.

The exhaustion of Maine’s 207 code is being driven by at least three factors, according to the PUC. First are numbers that have been assigned and are in use. Second are numbers that service providers are holding in their inventory based on expected need. Third are disconnected numbers that must be retained for a period before they can be given to new customers.