<P> Area code 978 was created as a split from area code 508 on September 1, 1997 and covers north central and most of northeastern Massachusetts (LATA code 128). Use of 978 became mandatory February 1, 1998 . Prior to when this area was served by 508 (July 1988), it was served only by the 617 area code, along with the rest of the eastern two - thirds of the state . 351 has been sharing the service area since May 2, 2001 . Since then, 10 digit local dialing is mandatory . </P> <P> Some mobile phone numbers from the 1990s assigned to rate centers in 978 and 351 kept the 508 area code just on those mobile lines after it was split . </P>

What state is area code 978 in usa