A state highway to be known as state route number 7 is established as follows:
Beginning at a junction with state route number 12 in the vicinity of Morton, thence northerly to a junction with state route number 706 at Elbe; also
From that junction with state route number 706 at Elbe, thence northerly to a junction with state route number 5 at Tacoma.
RCW 47.17.030