Area code 781 and 339 are telephone area codes in the North American Numbering Plan for the U.S. state of Massachusetts. The numbering plan area consists of Boston’s inner suburbs, known as the Route 128 corridor, and some outer suburbs, especially in the South Shore region. It was created as in an area code split of area code 617 on September 1, 1997.[1] Use of 781 became mandatory February 1, 1998.[2] Area code 339 is an overlay complex code for the same service area, activated on May 2, 2001.[3] Since then, ten-digit dialing has been mandatory.[3]
Some mobile telephone numbers assigned in the 1990s to rate centers in 781 and 339 kept the 617 area code just on those mobile lines after the split.