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  (I-5) twice west of Toledo.
SR 506 begins at the intersection of 2nd and Morse Streets in Ryderwood, a community in Cowlitz County. It travels north into Lewis County, then turns east past Vader to follow the Cowlitz River and interchange (I-5) twice west of Toledo.