city, seat of Hillsborough county, southern New Hampshire, U.S., lying along the Merrimack (Merrimack River) and Nashua rivers. It was settled about 1656 and was chartered in 1673 as Dunstable. It was a part of Massachusetts until a boundary settlement in 1741 placed it in New Hampshire. In 1803 the village of Indian Head, across the Nashua River, took the name of Nashua (allegedly derived from a local Indian tribe). The two settlements merged as Nashua in 1837. The northern section withdrew, as Nashville, in 1842 over a dispute in locating the town hall. They were reunited under a city charter in 1853. Since the closing of the textile mills after World War II, Nashua has developed a diversified industrial base. Its manufactures include computer products, electronic components, chemicals, office equipment, heavy machinery, and plastics. Nashua is the seat of Rivier College (founded 1933; Roman Catholic). A federal fish hatchery is in the city, and Silver Lake State Park is nearby. Pop. (1990) city, 79,662; Nashua PMSA, 168,233; (2000) city, 86,605; Nashua PMSA, 190,949.