 A 1900 map of the Tacoma area showed a roadway extending north from Spanaway to Tacoma that would later become SR 7 . In 1909 , the Alder @-@ Kosmos Road , numbered State Road 18 , was added to the state highway system and ran from Kosmos north through Morton and Elbe to Alder . The National Park Highway was created in 1913 and extended from the Pacific Ocean to Tacoma and south to Elbe , where it turned east into Mount Rainier National Park . Both highways were replaced by two branches of State Road 5 in 1923 , which traveled from Tacoma to Mount Rainier and Elbe to Chehalis . State Road 5 became Primary State Highway 5 ( PSH 5 ) during the creation of the Primary state highways in 1937 and the Tacoma – Mount Rainier branch remained the same , but the Elbe – Chehalis branch was shortened to Kosmos . 
