Washington State Route 9

State Route 9
SR 9 highlighted in red
Route information
Maintained by WSDOT
Length	98.17 mi[1] (157.99 km)
Existed	1964[2]–present
Major junctions
South end	SR 522 near Woodinville
Major intersections	SR 524 near Maltby US 2 near Snohomish SR 530 in Arlington SR 20 in Sedro-Woolley SR 542 in Deming
North end	Hwy 11 at Canada–US border in Sumas
Location
Country	United States
State	Washington
Counties	Snohomish, Skagit, Whatcom
Highway system
State highways in Washington Interstate US State Scenic Pre-1964 1964 renumbering Former
← SR 8 → SR 10

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.

Before SR 9 was created, several other roads used the route of the current highway. The first was a roadway extending from the current southern terminus to Snohomish established by 1895 and another road between Arlington and Sedro-Woolley by 1911. The current SR 542 concurrency was first established in 1925, when a branch of State Road 1 from Bellingham to Mount Baker was added to the state highway system. These roads were combined and several other roads were added to create Secondary State Highway 1A (SSH 1A), which originally ran from Woodinville to Blaine in 1937. A branch of SSH 1A connected the mainline to the Canada–US border in Sumas, but was later included into SSH 1A when the Blaine to Sumas segment was deleted in 1953. A highway renumbering in 1964 introduced the sign routes that would be co-signed with the existing system until 1970, one of which would replace SSH 1A, SR 9. SSH 1A / SR 9 extended south to Woodinville until 1965, when it was shortened to SR 202, later SR 522, which wasn't complete yet. SR 9 was not complete between Lake Stevens and Arlington until after 1966.

Between 2004 and 2009, nine complete construction projects, arranged by the Washington State Department of Transportation (WSDOT), have improved the roadway. The projects ranged from expanding the current weigh station at the Soper Hill Road intersection in 2005 to realigning the highway between Nooksack and Sumas in 2006 to eliminate 90-degree turns. WSDOT is also widening SR 9 in Snohomish County from 2 lanes to a four-lane divided highway. Between 2009 and 2013, WSDOT plans to complete six other projects in Snohomish County to improve the corridor from SR 522 to Bryant. Some projects include widenings, adding a roundabout at SR 531, realignments south of Snohomish and the addition of web cameras.