Washington State Route 506

State Route 506
SR 506 highlighted in red on a map of southwestern Washington.
Route information
Auxiliary route of I‑5
Defined by RCW 47.17.665
Maintained by WSDOT
Length:	11.53 mi (18.56 km)
Existed:	1964 – present
Major junctions
West end:	2nd Street in Ryderwood
	I‑5 southbound near Vader
East end:	I‑5 near Toledo
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 505 SR 507 →

State Route 506 (SR 506) is an 11.53-mile (18.56 km) long state highway in Cowlitz and Lewis counties, part of the U.S. state of Washington, serving the communities of Ryderwood and Vader. SR 506 begins at the intersection of 2nd and Morse Street in Ryderwood, a community in Cowlitz County, traveling north into Lewis County and turning east past Vader to parallel the Cowlitz River and interchange Interstate 5 (I-5) twice west of Toledo. Originating as Secondary State Highway 1P (SSH 1P) in 1937, the highway was designated in its current form in 1964 and it shared its eastern terminus with SR 505. SR 411 terminated at Vader and both SR 411 and SR 505 were moved away from SR 506 in 1991.

SR 506 begins as the continuation of Morse Street at the Second Street intersection in Ryderwood, a community located in the Campbell Creek valley in northern Cowlitz County. Traveling north to exit Ryderwood, the highway crosses Campbell Creek and enters Lewis County. The roadway parallels Stillwater Creek in its valley northeast and turns east to cross the creek into Vader. The street is named 7th Street after crossing Olequa Creek; SR 506 crosses a railroad track owned by BNSF Railway and used by two Amtrak services, the Cascades and Coast Starlight, between the Kelso and Centralia stations. Traveling east through Vader, 7th Street intersects the West Side Highway, formerly SR 411 until 1991, and leaves the city heading northeast, paralleling the Cowlitz River, to cross Lacamas Creek, the busiest segment of the highway at a daily average of 1,800 vehicles in 2008. The roadway crosses Bear Creek near its confluence with the Cowlitz River and interchanges Interstate 5 (I-5) southbound exit 59; the route turns north to interchange I-5 again at exit 60 in a full diamond interchange. Exit 60 is also the western terminus of the Toledo-Vader Road, formerly SR 505 until 1991.