Area Code 603 History:
Area code 603 was put into service.
Counties in New Hampshire within area code 603 include:
Belknap County, Carroll County, Cheshire County, Coos County, Grafton County, Hillsborough County, Merrimack County, Rockingham County, Strafford County, and Sullivan County.
Major cities or places in New Hampshire within area code 603 include:
Area code 603 serves the larger cities and communities of Amherst, Concord, Derry, Dover, Keene, Manchester, Nashua, Portsmouth and Rochester in addition to many smaller communities within the service area.