State Road No. 9 Olympic Highway began at Jct. State Road No. 1 Pacific Highway in Olympia and headed west to Mud Bay, then northerly via Shelton, Hoodsport, and Quilcene to Discovery Bay, then westerly to Sequim, Port Angeles, and Sappho, then southerly to Forks, Amanda Park, and Hoquiam to Aberdeen, then easterly to Montesano, Elma, and McCleary, ending at a junction with itself at Mud Bay.
In 1926, State Road No. 9 from Mud Bay via Port Angeles to Aberdeen became part of US 101. State Road No. 9 from Aberdeen via Montesano to Mud Bay became part of US 410. Both US 101 and US 410 followed State Road No. 9 from Mud Bay to Olympia. In 1937, State Road No. 9 was redesignated as Primary State Highway 9.
Port Townsend Branch
The Port Townsend Branch of State Road No. 9 Olympic Highway was added to the state highway system in 1923. It began at a junction with the trunk of of the Olympic Highway and headed northeasterly, ending at Port Townsend. This route was redesignated as the Port Townsend Branch of Primary State Highway 9 in 1937.
Elma-Grand Mound Branch
The Elma-Grand Mound Branch of State Road No. 9 Olympic Highway was added to the state highway system in 1925. This route was redesignated as the Elma-Grand Mound Branch of Primary State Highway 9 in 1937.
Primary State Hwys Secondary State Hwys
State Roads 1923-37