Area code 603 is the sole area code for the entire state of New Hampshire. It was established in 1947 as one of the original area codes and has never been split or overlaid, making it one of the few remaining single-code states in the U.S. Covering cities such as Manchester, Nashua, Concord, and Portsmouth, 603 is synonymous with New Hampshire’s tight-knit communities and rural charm. It is often used in local business branding and is a source of state pride. Despite technological growth and urban development, 603 continues to meet the state’s needs while serving as a symbol of tradition and unity.