Washington State Department of Highways; Rand McNally (1944). Highways of the State of Washington (Map). Olympia: Washington State Department of Highways. Retrieved July 2, 2017 – via David Rumsey Historical Map Collection.
"SR 520: Junction SR 202"(PDF). Washington State Department of Transportation. March 31, 2011. Retrieved June 3, 2017.
Washington State Department of Transportation (2014). Washington State Highways, 2014–2015(PDF) (Map). Olympia: Washington State Department of Transportation. Retrieved June 3, 2017. (Inset map)
"Chapter 51: State Highways—Route Numbers"(PDF). Session Laws of the State of Washington, 1970 1st extraordinary session. Washington State Legislature. February 24, 1970. pp. 367, 380. Retrieved June 1, 2017.
Washington State Department of Highways; Rand McNally (1939). Highways of the State of Washington (Map). Olympia: Washington State Department of Highways. Retrieved July 2, 2017 – via Washington Secretary of State.