[5] The roadway later intersects Pearl Street,[1] the only couplet on SR 507, which parallels Tower Avenue through Downtown Centralia.

[10] The busiest segment in 1970 was the Maple Street junction in Downtown Centralia, with an estimated daily average of 14,000 motorists.

[12] Sections of modern-day SR 507 were established as wagon roads as early as 1856, with the general corridor first appearing on maps in 1897.

[2][16] 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.

[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.