Dover is the oldest continuous settlement in New Hampshire and the seventh oldest in the United States. The permanent settlement occurred in what is now the Dover Neck area. For a few years Dover was an independent colony named Northam. In 1692 Northam became part of the Massachusetts Bay Colony. The original township of Dover included the present towns of Dover, Durham, Lee, Madbury, Somersworth, Rollinsford, and parts of Newmarket, Newington, and Greenland.
Dover has always used the Cocheco and Bellamy Rivers to its economic advantage. The first use of the water power of the Cocheco River was in 1642, when a sawmill was built. In the 1700s Dover had an extensive shipbuilding industry. By 1830, the city had become a leading manufacturer of cotton goods in the country, using the river to power several mills. Later in the nineteenth century, a brick industry flourished and shoe manufacturing developed in the 1900's.