MP: .11 Location: Spirit Lake Memorial Hwy and I-5, Castle Rock Reassurance shield at the beginning of SR 504 MP: 3.6 Location: Spirit Lake Memorial Hwy and S Silver Lake Rd, Cowlitz Cty Reassurance shield after the turnoff down to Silver Lake Rd. We have already started our ascension- we’ll move from sea level to … Continue reading State Route 504, I-5/SR 411 to SR 505