State Route 12 (SR 12) is a state highway in the U.S. state of California that travels in an east–west direction from SR 116 in Sebastopol in Sonoma County to SR 49 just north of San Andreas in Calaveras County. The route connects the Sonoma and Napa valleys with the Sacramento–San Joaquin River Delta and the Sierra Foothills. It is constructed to freeway standards from the Fulton Road/South Wright Road stoplight in Santa Rosa, to its partial interchange with Farmers Lane (also in Santa Rosa).
Route description
thumb|left|SR 12 runs along Broadway in Sonoma.
thumb|left|SR 12/SR 113 roundabout
thumb|left|SR 12 runs along Kettleman Lane in Lodi.
thumb|left|SR 12 between Lodi and Jackson
There are six segments that are overlaps with other highways: in the Napa and Sonoma valleys with SR 121, in the southern Napa Valley with SR 29, a short overlap with I-80 at Cordelia Junction in Fairfield, another short overlap with SR 99 in Lodi, and overlaps with SR 88 and SR 26 in the Sierra foothills. The highway is mainly two lane rural highway, with the exception of short segments in Santa Rosa and Fairfield/Suisun City, the overlaps with I-80 and SR 99, and segments within developed areas, such as Santa Rosa and Lodi.
SR 12 begins in the west at its junction with SR 116 in Sebastopol. After passing east through Santa Rosa on a mix of freeway, surface street, and expressway, it turns south into the Sonoma Valley, passing the Jack London State Historic Park at Glen Ellen. It winds through Sonoma on surface streets, where the historic Vallejo Estate and Sonoma Mission, both part of the Sonoma State Historic Park, are. and in Sebastopol, from US 101 to Sonoma, and from I-80 to SR 88 is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration. SR 12 is eligible to be included in the State Scenic Highway System; however, it is only designated as a scenic highway from its intersection with Danielli Avenue east of Santa Rosa to its junction with London Way near Agua Caliente, meaning that it is a substantial section of highway passing through a "memorable landscape" with no "visual intrusions", where the potential designation has gained popular favor with the community.
SR 12 has been designated by various state laws and through local usage as the Valley of the Moon Scenic Route (the portion running through Sonoma County, though the first sign with this name is at the intersection of Farmers Lane and Fourth Street in Santa Rosa); Luther Burbank Memorial Highway from Santa Rosa to Sebastopol (after botanist Luther Burbank).
SR 12 is also known as Sonoma Highway between Santa Rosa and the west side of the city of Sonoma;
Broadway between Sonoma Plaza and its junction with SR 121 in Schellville;
Carneros Highway for the length of its concurrency with 121 between Schellville and its junction and the north end of its concurrency with SR 29 near Napa;
Jameson Canyon Road from where its concurrency with SR 29 ends in American Canyon to its junction with I-80 in Cordelia;
and Rio Vista Highway from I-80 to SR 160 east of Rio Vista, and informally as "Blood Alley" from Lodi to Fairfield. The segment through Lodi to the overlap with SR 99 is on Kettleman Lane.
History
Before the 1964 renumbering, this route was signed as Sign Route 12 for most of its length. However, SR 12 was designated as Legislative Route 51 (LR 51) from SR 116 to SR 121 before the 1964 renumbering. Portions of the route from SR 29 to I-80 ran concurrently with State Route 29 and State Route 37; this was also LR 8 and a former routing of US 40. The portion from I-80 to then-US 99 was designated as LR 53 in 1919; from US 99 to SR 49, it was designated as LR 24.
In 1976, the discontinuity resulting from the concurrency with State Route 84 was removed.
Future extension
Plans call for a western extension of its western terminus to SR 1 near Bodega Bay. Plans also called for Route 12 to be built as a freeway from Farmers Lane to Melita Road, in Santa Rosa; however, as of 2014, this project was delayed due to community opposition.