This is a map of the state highways in Washington as they existed in 1970, just before the old primary-secondary split was removed. Primary routes are red and secondary routes are purple. Thin orange is just current routes. Email me if you would like a copy of the GIS data I created for the highways.
No machine-readable source provided. Own work assumed (based on copyright claims).
No machine-readable author provided. NE2 assumed (based on copyright claims).