 Sunbury is the largest principal city of the Sunbury-Lewisburg-Selinsgrove, Pennsylvania, a Combined Statistical Area that includes the Sunbury (Northumberland County), Lewisburg (Union County), and Selinsgrove (Snyder County) micropolitan areas, which had a combined population of 173,726 at the 2000 census.As of the census of 2010, there were 9,905 people, 4,540 households, and 2,637 families residing in the city.The population density was 4,716.7 people per square mile.