- State Route 9 (SR 9) is a 98.17-mile (157.99 km) long state highway traversing three counties, Snohomish, Skagit, and Whatcom, in the U.S. state of Washington. The highway extends north from an interchange with SR 522 in the vicinity of Woodinville north through Snohomish, Lake Stevens, Arlington, Sedro-Woolley, and Nooksack to become British Columbia Highway 11 (BC 11) at the Canada–US border in Sumas. Three other roadways are briefly concurrent with the route: SR 530 in Arlington, SR 20 in Sedro-Woolley, and SR 542 near Deming. A spur route in Sumas serves trucks traveling into British Columbia.