U.S. Federal Route 11 runs east-west across Central Northumberland County. It runs from the Northumberland/Union County Line, south of Northumberland, to the Northumberland/Montour County Line, near Danville. U.S. Rt. 11 passes through the following towns in Northumberland County. Northumberland
NB U.S. Rt. 11 at the Union/Northumberland County Line. SB U.S. Rt. 11 at the West Branch of the Susquahanna River. SB U.S. Rt. 11/NB PA St Rt 405 at Queen Street. SB U.S. Rt. 11 at north PA St Rt 405. A set of guide markers on SB PA St Rt 405.