Washington State Route 203

State Route 203
A map of Washington's highway system in the Seattle metropolitan area with SR 203 highlighted in red.
Route information
Auxiliary route of US 2
Defined by RCW 47.17.390
Maintained by WSDOT
Length:	24.26 mi (39.04 km)
Existed:	1964 – present
Major junctions
South end:	SR 202 in Fall City
North end:	US 2 in Monroe
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 202 SR 204 →

State Route 203 (SR 203) is a Washington state highway in King and Snohomish counties. The 24.26-mile (39.04 km) route begins at an intersection with SR 202 in Fall City. The highway extends north past Carnation and Duvall to end at U.S. Route 2 (US 2) in Monroe. The roadway connects Fall City, Carnation, Duvall and Monroe, all located along the Snoqualmie River, which SR 203 roughly parallels.

The route originally was divided into four separate roads, Fall City–Carnation, Carnation–Duvall, Duvall–Monroe and Lewis Street. The first road to be paved, Lewis Street in Monroe, was completed in 1912; the roads were later combined to form Secondary State Highway 15B (SSH 15B) in 1937. SSH 15B was later renumbered to SR 203 in 1964 during the highway renumbering. The routing of SR 203 was suggested as a new freeway in the 1990s and 2000s.

State Route 203 (SR 203) begins its 24.26 miles (39.04 km) of highway at an intersection with SR 202, a primarily west–east route, in Fall City. There, the road is named the Fall City–Carnation Road and travels northwest, paralleling the former route of the Monroe–Tanner route operated by the Chicago, Milwaukee, St. Paul and Pacific Railroad. After bridging the Rutherford Slough twice, the route travels closer to the shoreline of the Snoqualmie River. SR 203 runs north past Northeast Tolt Hill Road to cross the Tolt River into Carnation. Leaving Carnation, the highway becomes the Carnation–Duvall Road and intersects Carnation Farm Road before curving west to intersect Stillwater Hill Road. Eventually, the roadway continues the original northern route past the 124th Street roundabout into Duvall. In Duvall, SR 203 intersects the Woodinville–Duvall Road and Cherry Valley Road before curving along the Snoqualmie River shoreline into Snohomish County. After leaving Duvall and King County, SR 203 becomes the Duvall–Monroe Road and travels north to cross the Skykomish River and enter Monroe as Lewis Street. In Monroe, the highway parallels Woods Creek and intersects Main Street near the Monroe Greyhound Lines station. After Main Street, the road crosses the BNSF Railway Everett–Spokane line and ends at an intersection with U.S. Route 2 (US 2) and Chain Lake Road. South of the US 2 intersection, an estimated 15,000 motorists used Lewis Street daily in 2007 based on average annual daily traffic (AADT) data collected by the Washington State Department of Transportation.