The road begins in Boonville at an at-grade intersection with SR 128. The road heads eastward through a forested and mountainous area for approximately fifteen miles before entering the Russian River Basin, where numerous farms exist. The road ends with an interchange with U.S. Route 101 in southern Ukiah.[2]
This route, under the name of the Ukiah-Boonville Road, has been in use as a road since at least 1897, when it was the scene of the robbery of a stage coach carrying the payrolls for a coastal lumber mill.[5] However, it was not a state highway until 1963, when it was added to the state highway system. It was given its present number in the 1964 state highway renumbering.
Major intersections
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 Mendocino 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 4, 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.
^Palmer, Lyman L. (1967), History of Mendocino County, California, comprising its geography, geology, topography, climatography, springs and timber, Mendocino County Historical Society, p. 738.
^California Department of Transportation (July 2007). "Log of Bridges on State Highways". Sacramento: California Department of Transportation.