Sunbury, city (1990 pop. 11,591), seat of Northumberland co., E central Pa., on the Susquehanna River at the confluence of its north and west branches; laid out 1772, inc. 1921. It is in an agricultural area with grain, apples, livestock, and dairying. Foods, fiberboard insulation, steel wire and cable, apparel, textiles, and wood products are manufactured. The city was the site of a Native American village in the early 18th cent. In 1742 a mission was established, and in 1756 Fort Augusta was built (parts of the fort still stand). Thomas A. Edison worked in Sunbury. On the Susquehanna is a large "fabridam"—a dam of a fabric that can be collapsed and inflated.