State Route 507 (SR 507) begins at a diamond interchange with Interstate 5 (I-5), co-signed as U.S. Route 12 (US 12) in Centralia.[3] Traveling east as Mellen, Alder and West Cherry Streets,[1] the highway crosses railroad tracks owned by BNSF Railway and used by Amtrak's Cascades and Coast Starlight routes,[4] both of which serve the Centralia Amtrak station.[5] The roadway later intersects Pearl Street,[1] the only couplet on SR 507, which parallels Tower Avenue through Downtown Centralia.[6] The street then becomes Tower Avenue and turns north to pass the Centralia Amtrak station.[1] SR 507 realigns west as Sixth Street to intersect and become Pearl Street, once again traveling northeast as Downing Road to leave Centralia.[1] Still parallel to BNSF Railway tracks,[4] the road leaves Lewis County, enters Thurston County, passes Bucoda and turns north to intersect an old segment of US 99 in Tenino. Within Tenino, the highway stops paralleling the BNSF tracks and goes east through the city as Sussex Avenue and starts to parallel a route of the Tacoma Rail eastward out of the city.[4] Passing through Rainier as Binghampton Street, the roadway intersects the eastern terminus of SR 510 in Yelm and then turns southeast as Yelm Avenue,[1] before leaving both Yelm and Thurston County to enter Pierce County on a bridge over the Nisqually River. Once in Pierce County, SR 507 intersects SR 702 in McKenna and continues north as the Spanaway McKenna Highway to Roy, where the highway turns east and then northeast into Fort Lewis. Immediately after leaving Fort Lewis, the roadway ends at an intersection with SR 7 in Spanaway.[7][8][9] Between SR 510 in Yelm and SR 702 in McKenna, the roadway had an estimated daily average of 19,000 motorists in 2007, causing the segment to be the busiest on SR 507.[10] The busiest segment in 1970 was the Maple Street junction in Downtown Centralia, with an estimated daily average of 14,000 motorists.[11] SR 507 is also the southern segment of the East Pacific Highway, which runs from Centralia to Sumas.[12]
WSDOT began construction of safety improvements to a section of SR 507 between Roy and Yelm in 1985 following a higher-than-average rate of collisions, especially those involving trees. Approximately 50 to 70 fir trees were removed to improve visibility despite opposition from local residents seeking to keep the highway's scenic qualities.[17] The highway's bridge over the Nisqually River in McKenna was replaced by a new span in 1987.[18] A left turn lane was installed at the Yew Street intersection east of the Interstate 5 (I-5) and U.S. Route 12 (US 12) interchange in Centralia on May 24, 2007.[19]SR 704, when completed, is predicted to reduce congestion on SR 507.[20] A section of the highway near Rainier was renamed the Sgt. Justin. D. Norton Memorial Highway in 2017 to honor a local soldier.[21]
^Washington State Highways, 2008–2009(PDF) (Map) (2008–09 ed.). 1:842,000. Cartography by United States Geological Survey. Washington State Department of Transportation. 2008. § E3, F3. Retrieved July 17, 2009.
^Washington State Legislature (March 18, 1937). "Chapter 207: Classification of Public Highways". Session Laws of the State of Washington (1937 ed.). Olympia, Washington: Washington State Legislature. p. 103. Retrieved July 17, 2009. (g) Secondary State Highway No. 5H; beginning at a junction with Primary State Highway No. 5 in the vicinity south of Tacoma, thence in a southwesterly direction by the most feasible route by way of McKenna, Yelm, and Rainier, to Tenino to [on] Primary State Highway No. 1.
^Washington State Legislature (March 20, 1943). "Chapter 212: Public Highways". Session Laws of the State of Washington (1943 ed.). Olympia, Washington: Washington State Legislature. p. 661. Retrieved July 17, 2009. (n) Secondary State Highway No. 1N; beginning at Tenino, thence in a southerly direction by the most feasible route by way of Bucoda to the north corporate limits of the city of Centralia.
^C. G. Prahl (December 1, 1965). "Identification of State Highways"(PDF). Washington State Highway Commission, Department of Highways. Retrieved July 17, 2009.
