The lifespan of Maine’s 207 area code has been extended, and the three-digit prefix is now expected to be used in new telephone numbers until 2029.

The Maine Public Utilities Commission has been taking steps to conserve the supply of available phone numbers with the state’s current area code, in use since 1947. Once all the numbers are assigned, the state would have to come up with another area code for new phone numbers, meaning callers would have to dial an area code when making some in-state calls.

Maine is one of only a dozen states with a single area code.

In 2021, the commission said the 207 numbers would be exhausted in 2025, but that time frame was later extended to early 2027. On Wednesday, the commission extended the prediction to the second quarter of 2029.

One of the steps the PUC has taken makes it easier for phone service providers to donate numbers to each other, no longer requiring that the numbers be moved in blocks of 10,000. The commission also has worked with providers to return blocks of unused numbers in groups of 1,000.

The PUC said the efforts have resulted in the return of more than 750,000 numbers from unused or lightly used blocks of numbers.

“Since we first became aware of the risk to Maine’s 207 area code, two things have become clear: that preserving the area code is important to the people of Maine and that we have the tools to help do so,” PUC Chair Philip L. Bartlett II said in a statement. “Our staff is dedicated to preserving Maine’s single area code for as long as possible.”

The PUC said one of the reasons the area code is becoming exhausted is an increase in the number of phone service providers, who are issued blocks of numbers to provide to customers. The commission said Maine’s efforts have served as a model for other states facing area code exhaustion.