Massachusetts currently utilizes 9 area codes. When first established by AT&T and the Bell System in 1947, 413 covered western Massachusetts including Springfield and 617 covered eastern Massachusetts including Boston. The most recently added was 339 in 2001 as an overlay to 781. Today, 508 is the most populated with an estimated 1.8 million of the state's 6.5 million residents.
Sources: North American Numbering Plan Administration (NANPA), telecom providers, and the U.S. Census Bureau.