Sunbury is a city and the county seat of Northumberland County in Pennsylvania, United States. Located in the Susquehanna Valley, Sunbury is positioned on the east bank of the Susquehanna River. Sunbury's roots stretch back to the early 18th century. As of the 2010 census, it had a population of 9,905. The city is one of the three principal cities in the larger Bloomsburg-Berwick-Sunbury, PA Combined Statistical Area. Sunbury is connected to inventor Thomas Edison.