is northumberland a county
Northumberland County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 94,528. Its county seat is Sunbury.The county was formed in 1772 from parts of Lancaster, Berks, Bedford, Cumberland, and Northampton Counties and named for the county of Northumberland in northern England.ccording to the U.S. Census Bureau, the county has a total area of 478 square miles (1,240 km 2), of which 458 square miles (1,190 km 2) is land and 19 square miles (49 km 2) (4.0%) is water. The main river in Northumberland County is the Susquehanna River.