Washington State Route 506

Traveling north to exit Ryderwood, the highway crosses Campbell Creek and enters Lewis County.

[2][19][20] An extension of the highway connecting Vader to SR 407 near Cathlamet was studied by the state legislature in 1973 but was not recommended for construction.

[8] The Washington State Transportation Improvement Board heard proposals in the early 1990s to decommission SR 506 and transfer control of the highway to the counties and local governments, which was opposed by residents due to high maintenance costs.

[24][25] The overpass carrying SR 506 over I-5 was closed on July 6, 2021, after a truck struck it and caused major structural damage.

Governor Jay Inslee declared a state of emergency and approved funds to replace the entire bridge.

SR 506 at its western terminus in Ryderwood
Secondary State Highway 1P (1937-1964), which preceded current SR 506 (1964-present), seen on a topographic map of Hoquiam, Washington produced by the United States Geological Survey in 1951; the road followed the Longview, Portland and Northern Railway until 1953.
The predecessor to SR 506, Secondary State Highway 1P (SSH 1P), pictured in a topographic map paralleling the Longview, Portland and Northern Railway in 1951.