Northumberland -- U.S. County in Pennsylvania Population (2000): 94556 Housing Units (2000): 43164 Land area (2000): 459.910657 sq. miles (1191.163083 sq. km) Water area (2000): 17.468738 sq. miles (45.243823 sq. km) Total area (2000): 477.379395 sq. miles (1236.406906 sq. km) Located within: Pennsylvania (PA), FIPS 42 Location: 40.863236 N, 76.687307 W Headwords: Northumberland Northumberland, PA Northumberland County Northumberland County, PA