Reported (603) XXX-XXXX phone numbers lookup

Area Code 603 History and Coverage

The code 603 was introduced in 1947 as part of the first deployment of the North American Numbering Plan. The original plan had 86 area codes assigned within the United States and Canada. There was only one designation for New Hampshire, which was a state of moderate size without a major metropolitan area like Boston or New York.

Rapid growth during the years following World War II created additional strain on the number of available phone numbers, especially in the southern counties closer to Massachusetts. Development on Interstate 93 and the Everett Turnpike meant more development and thus more need for numbers, but mobile phone service was also becoming popular. These trends did not impact northern counties or the interior of the state as much.

Despite this growth, 603 has not undergone a geographic split or received an overlay. That continuity differs from many original codes that were later divided or supplemented as numbering demand increased. The long-standing arrangement has accommodated sharply different settlement patterns, from developed border communities to rural areas in the north. Coos County extends to the Canadian border.