California State Route 12

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.[4][5]

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.[4][5]

South of Sonoma, SR 12 turns east, joining SR 121 for nearly nine miles, then turns south briefly as it leaves SR 121 and joins the four-lane expressway SR 29 to cross the Napa River. Four miles after joining SR 29 it splits off towards the east on Jameson Canyon Road; this section is also the 1928 re-alignment of the Lincoln Highway, the first road across America. After a brief merge with Interstate 80, SR 12 branches off to the east as an expressway through Fairfield and Suisun City. East of Suisun it becomes two lanes again and crosses south of Travis Air Force Base, through rolling fields with numerous wind turbines. Just past Braid's Bridge is the Western Railway Museum. At Rio Vista, SR 12 crosses the Helen Madere Memorial Bridge over the Sacramento River, entering the California Delta.[4][5]

This stretch of the river has twice been the site of much-publicized inland excursions by humpback whales, presumably veering off course while making their annual migrations along the Pacific coast. In 1985 Humphrey the whale swam about as far as the Rio Vista Bridge. In 2007 a humpback mother and calf dubbed Delta and Dawn circled for several days just upstream of the bridge, seemingly reluctant to pass under it again after having spent the previous three or four weeks upriver near Sacramento.

From the Sacramento River to the junction with Interstate 5, SR 12 crosses several of the waterways of the California Delta and the low-lying fields between them. Through Lodi it becomes a wide four-lane business route. After another brief merger with another freeway, this time SR 99, SR 12 heads east into the Sierra foothills (with shared segments with SR 88 and SR 26) before ending at the junction with SR 49 just north of San Andreas.[4][5]

SR 12 is part of the California Freeway and Expressway System,[6] and from I-80 to SR 88 is part of the National Highway System,[7] a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.[8] SR 12 is eligible to be included in the State Scenic Highway System;[9] 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,[10] 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.[11]

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);[12] Luther Burbank Memorial Highway from Santa Rosa to Sebastopol (after botanist Luther Burbank).[13] 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;[14] 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,[15][16] and informally as "Blood Alley" from Lodi to Fairfield.[17] The segment through Lodi to the overlap with SR 99 is on Kettleman Lane.[4]

Route 12 between Lodi and Jackson

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 or with 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.[18]

In 1976, the discontinuity resulting from the concurrency with State Route 84 was removed.[18]

Plans call for a western extension of its western terminus to State Route 1 near Bodega Bay.[19] 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.[20]

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 an overlap due to a correction or change, and T indicates postmiles classified as temporary (for a full list of prefixes, see the list of postmile definitions).[21] Segments that remain unconstructed or have been relinquished to local control may be omitted. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.

County	Location	Postmile [21][1][22]	Exit [23]	Destinations	Notes
Sonoma SON 9.12-41.36	Sebastopol	9.12		Bodega Avenue – Bodega Bay	Continuation beyond SR 116
		9.12		SR 116 (Petaluma Avenue, Main Street) – San Francisco, Jenner	West end of SR 12
	Santa Rosa	R12.94		Fulton Road, Wright Road
		​	West end of freeway
		R14.45	5	Stony Point Road
		R15.30	6	Dutton Avenue
		R16.04	7A	US 101 – San Francisco, Eureka	Signed as exits 7A (south) and 7B (north) westbound; US 101 exits 488B
		R16.63	7B	South E Street – Downtown Santa Rosa	Signed as exit 7C westbound
		​	East end of freeway
		T17.53		Farmers Lane
	Schellville	41.36 7.44[N 1]		SR 121 south (Fremont Drive) – Petaluma, San Francisco	West end of SR 121 overlap
Napa NAP 0.00-3.31	Napa	R4.47[N 1] R8.66[N 2]		SR 29 north / SR 121 north – Napa, Calistoga	East end of SR 121 overlap; west end of SR 29 overlap
	​	R6.20[N 2]		SR 221 / Soscol Ferry Road – Downtown Napa, Lake Berryessa
	​	4.71 0.00[N 2]		SR 29 south / Airport Boulevard – Vallejo, Napa County Airport	East end of SR 29 overlap
Solano SOL 0.00-26.41	Fairfield	R2.79 R11.98[N 3]		I-80 west – San Francisco	West end of I-80 overlap; westbound exit and eastbound entrance; I-80 east exit 39/Red Top Road, west exit 39B
		​	West end of freeway on I-80
		12.74[N 3]	40	Green Valley Road	Westbound exit is part of exit 41
		12.84[N 3]	40	I-680 south – Benicia, Martinez, San Jose	I-680 north exits 17A-B
		13.49[N 3]	41	Suisun Valley Road, Pittman Road
		15.82[N 3] L1.80		I-80 east – Sacramento	East end of I-80 overlap; eastbound exit and westbound entrance; I-80 west exit 43
		L2.22	56	Chadbourne Road to I-80 east – Fairfield Auto Mall, Sacramento
		​	East end of freeway
	Suisun City	R4.47	58A	Webster Street, Jackson Street – Fairfield	Interchange
		R4.57	58B	Main Street – Suisun City Business District	Interchange
	​	19.17		SR 113 north / Birds Landing Road – Dixon, Birds Landing, Collinsville
	Rio Vista	26.28		SR 84 / Front Street – Rio Vista, Ryer Island	Interchange
Solano–Sacramento county line	Rio Vista city limit		Rio Vista Bridge over the Sacramento River
Sacramento SAC 0.00-6.20	​	0.57		SR 160 (River Road) – Isleton, Sacramento, Antioch
San Joaquin SJ 0.00-27.64	​	10.17		I-5 – Sacramento, Stockton, Los Angeles	Interchange; I-5 exit 485
	​	10.30		CR J8 (Thornton Road)
	Lodi	15.16		CR J10 (Lower Sacramento Road) – Woodbridge
		16.93		CR J3 (Hutchins Street)
		17.95		SR 99 Bus. (Cherokee Lane) – Central District	Former US 50 / US 99
		18.07 29.50[N 4]		SR 99 south / Kettleman Lane – Fresno, Los Angeles	Interchange; west end of SR 99 overlap; SR 99 north exit 264B, south exit 264B
		​	West end of freeway on SR 99
		​	East end of freeway on SR 99
		30.97[N 4] 18.08		SR 99 north / Victor Road – Sacramento, Central Lodi	Interchange; east end of SR 99 overlap; SR 99 exit 266
	Lockeford	L23.29 L12.24[N 5]		SR 88 west / Victor Road – Stockton	West end of SR 88 overlap
		13.60[N 5]		CR J5 (Jack Tone Road)	West end of CR J5 overlap
		14.08[N 5]		CR J5 (Elliott Road) / Tully Road	East end of CR J5 overlap
	Clements	19.17[N 5] 23.17		SR 88 east – Ione, Jackson, Lake Tahoe	East end of SR 88 overlap
Calaveras CAL 0.00-18.20	Valley Springs	9.93		SR 26 west / Laurel Street – Linden, Campo Seco, Pardee Reservoir, Lake Amador	West end of SR 26 overlap
	​	13.87		SR 26 east / Toyon Circle – Mokelumne Hill	East end of SR 26 overlap
	​	18.20		SR 49 – Mokelumne Hill, San Andreas	East end of SR 12
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

•  California Roads portal
• Bliss (image)

• California @ AARoads.com – State Route 12
• Caltrans: Route 12 highway conditions
• California Highways: Route 12

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