The road begins with a complex interchange at U.S. Route 101 just north of Arcata, where entrance to US 101 and exit from the freeway are slightly separated. The road then heads eastward through a forested area in the Azalea State Reserve just north of the Mad River. The road continues to parallel the river with various roads branching off it until it reaches its eastern terminus at State Route 299, the Trinity Scenic Byway, with an interchange.[2]
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage. R reflects a realignment in the route since then, M indicates a second realignment, L refers to an overlap due to a correction or change, and T indicates postmiles classified as temporary (for a full list of prefixes, see California postmile § Official postmile definitions).[1] Segments that remain unconstructed or have been relinquished to local control may be omitted. The entire route is in Humboldt County.
^ abcCalifornia Department of Transportation. "State Truck Route List". Sacramento: California Department of Transportation. Archived from the original(XLS file) on September 5, 2015. Retrieved June 30, 2015.
^Federal Highway Administration (March 25, 2015). National Highway System: California (North)(PDF) (Map). Scale not given. Washington, DC: Federal Highway Administration. Retrieved September 16, 2017.
^Natzke, Stefan; Neathery, Mike & Adderly, Kevin (June 20, 2012). "What is the National Highway System?". National Highway System. Washington, DC: Federal Highway Administration. Retrieved July 1, 2012.
^California Department of Transportation (July 2007). "Log of Bridges on State Highways". Sacramento: California Department of Transportation.