Washington State Legislature (March 4, 1915). "Chapter 29: Re-Location of the Sunset Highway". Session Laws of the State of Washington (1915 ed.). Olympia, Washington: Washington State Legislature. pp. 64–65. Retrieved February 18, 2013.
Washington State Legislature (March 14, 1919). "Chapter 110: Amending Highway Classification Act". Session Laws of the State of Washington (1919 ed.). Olympia, Washington: Washington State Legislature. pp. 267–270. Retrieved February 18, 2013.
Washington State Legislature (March 19, 1923). "Chapter 185: Primary and Secondary State Highways". Session Laws of the State of Washington (1923 ed.). Olympia, Washington: Washington State Legislature. p. 627. Retrieved February 18, 2013.
Washington State Legislature (March 17, 1937). "Chapter 190: Establishment of Primary State Highways". Session Laws of the State of Washington(PDF) (1937 ed.). Olympia, Washington: Washington State Legislature. p. 934. Retrieved February 18, 2013.