 A 1923 restructuring of the system re @-@ assigned numbers to almost all the primary state highways . State Road 5 became a primary route and was greatly expanded , taking over the entire McClellan Pass Highway and the National Park Highway east of the Pacific Highway . The former secondary State Road 5 was realigned starting from near Packwood , heading north instead of east , alongside the <unk> River to the old McClellan Pass Highway at Cayuse Pass , west of the summit of the Cascades . The new State Road 5 , named the National Park Highway System , now included four roads in the vicinity of Mount Rainier National Park , but as the road across the Cascades at Chinook Pass was not yet built , these roads did not connect with each other . Also included in this numbering was the designation of the Inland Empire Highway , including Yakima to Clarkston , as State Road 3 . In 1925 , a spur was added to State Road 9 — the Olympic Highway , looping around the Olympic Peninsula — connecting Elma to the Pacific Highway at Grand Mound , and creating a shortcut between the Cowlitz River route and Aberdeen . The Olympic Highway from Elma west to Aberdeen had been added to the state highway system in 1905 west of and 1913 east of Montesano . 
