A state highway to be known as state route number 507 is established as follows:
Beginning at a junction with state route number 5 in Centralia, thence northerly by the most feasible route by way of Bucoda to Tenino, thence northeasterly by way of Rainier, Yelm and McKenna to a junction with state route number 7 in the vicinity south of Tacoma.
RCW 47.17.670