Area code 351 is an overlay of 978, serving northeastern Massachusetts, including cities like Lowell, Lawrence, and Gloucester. It was introduced in 2001 to provide additional number availability in a region known for its colonial history, education, and proximity to the Boston metro area. Ten-digit dialing is required throughout the region. While 978 is the more established identifier, area code 351 has gained traction in business, residential, and academic circles. It represents the balance between historic charm and modern growth in one of New England’s most culturally rich corridors.