SR 599 was built as a southern extension of the West Marginal Freeway circa 1970. SR 599 starts at I-5 Exit 156 and heads NW to Jct SR 99 at the Pacific Hwy S (aka Tukwila International Blvd) interchange. SR 599 is 1.75 miles long.
This route had been added to the state highway system in 1957 as part of the West Marginal branch of PSH 1 although it did not open to traffic until much later as stated above.
Primary State Hwys Secondary State Hwys