Two different routes were designated as SSH 1N at different times between 1937 and 1970.
The Earlier SSH 1N
The earlier SSH 1N was added to the state highway system in 1937. This route started at Jct PSH 1 (US 99) just north of Chehalis and headed westerly and northerly, ending at Jct PSH 9 (now US 12) in Rochester. This route was dropped from the state highway system in 1953.
The Later SSH 1N
At the time that the earlier SSH 1N was dropped from the state highway system, another highway was added as SSH 1N. This later route started at Jct SSH 5H in Toledo and headed SSW via Bucoda, ending at the northern city limits of Centralia. 1959 legislation reversed the description and extended SSH 1N from the north city limits via Downtown Centralia to Jct PSH 1 (US 99, now I-5) at Exit 81. Today, SSH 1N is part of SR 507.
Primary State Hwys Secondary State Hwys