California State Route 20

State Route 20 (SR 20) is a state highway in the northern-central region of the state of California, running east–west north of Sacramento from the North Coast to the Sierra Nevada. Its west end is at SR 1 in Fort Bragg, from where it heads east past Clear Lake, Colusa, Yuba City, Marysville and Nevada City to I-80 near Emigrant Gap, where eastbound traffic can continue on other routes to Lake Tahoe or Nevada.

"CA 20" redirects here. For the congressional district, see California's 20th congressional district.

State Route 20
SR 20 highlighted in red
Route information
Defined by Streets and Highways Code § 320
Maintained by Caltrans
Length211.882 mi[1] (340.991 km)
(plus about 15.5 mi (25 km) on US 101)
HistoryState highway in 1910–1919; numbered in 1934
Tourist
routes		 Yuba-Donner Scenic Byway
RestrictionsNo hazardous material along the northeast shore of Clear Lake between SR 29 and SR 53[2]
Major junctions
West end SR 1 in Fort Bragg
 
East end I-80 near Emigrant Gap
Location
CountiesMendocino, Lake, Colusa, Sutter, Yuba, Nevada, Placer
Highway system
← SR 19SR 22 →

Portions of SR 20 are built near the routing of what was first a wagon road and later a turnpike in the late 19th century. This road was extended through the state highway system all the way to Ukiah in the early 20th century, and the missing link near Clear Lake was completed in 1932 before the official designation of this highway as SR 20 in 1934. There have been subsequent improvements to the road, such as the conversion of the Grass Valley portion of the route to freeway standards.

Route description

State Route 20 begins at SR 1 in southern Fort Bragg, less than 1 mile (1.6 km) from the Pacific Ocean. It heads east, quickly climbing into the Mendocino Range along a ridge and crossing through Dunlap Pass. The highway continues to rise alongside the North Fork Big River and tributaries, crossing another summit and then descending to Willits in the Little Lake Valley via Broaddus Creek. An overlap with US 101 begins in Willits and heads southeasterly to Calpella, north of Ukiah in Redwood Valley. There SR 20 turns east again, crossing the Russian River, passing the north shore of Lake Mendocino, and rising to a summit via the East Fork Russian River and Cold Creek. The roadway again descends alongside the Blue Lakes and Scotts Creek to the junction with SR 29 and the settlement of Upper Lake in the Clear Lake Basin. SR 20 closely follows the northeast shore of Clear Lake, staying right above the water line to avoid the adjacent hills. Where the lake ends, SR 20 continues east, intersecting SR 53 and then following the North Fork Cache Creek and tributaries to the Lake-Colusa County line. During its final descent into the Sacramento Valley, SR 20 intersects SR 16 and curves north and back east, entering the valley via Salt Creek.[3]

SR 20 in the Sacramento Valley

Once it enters the flat Sacramento Valley, SR 20 takes a generally straight path, crossing I-5 in Williams, overlapping SR 45 near the west bank of the Sacramento River southeast from Colusa, and then turning back east to cross the Sacramento River and Sutter Bypass on its way to Yuba City. The route crosses SR 99 west of central Yuba City, and runs east through northern Yuba City to the Feather River, which it crosses on the 10th Street Bridge into Marysville. Within the central part of that city, SR 20 makes several turns, first turning south from 10th Street onto E Street, then east on 9th Street (overlapping SR 70), north on B Street, and east on 12th Street (splitting from SR 70). The highway leaves Marysville to the northeast, paralleling the Yuba River on its north side as it enters the foothills of the Sierra Nevada.[3]

SR 20 rises into the Sierra along the north side of the Yuba River, crossing to the south side near Smartsville and then climbing through several ravines to the Penn Valley. The current alignment, built in the mid-1980s as a mostly two-lane freeway, continues east across rugged terrain to the city of Grass Valley, where it joins SR 49 on the Golden Center Freeway. The two routes travel northeast to Nevada City, where SR 49 turns northwest and SR 20 resumes its eastward course as a two-lane highway. The roadway climbs from Nevada City and follows Harmony Ridge and Washington Ridge before descending into the Bear Valley via a series of hairpin turns, and then climbing, just north of Emigrant Gap, to its end at I-80 at Yuba Pass.[3] The Pioneer Trail, a National Recreation Trail, parallels SR 20 from a point on Harmony Ridge to the Bear Valley, and includes parts of a branch of the California Trail first used in 1850.[4]

SR 20 east of US 101 is part of the California Freeway and Expressway System,[5] although it is mostly a two-lane surface road; east of SR 53, it is part of the National Highway System,[6] a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.[7] All of SR 20 is on the Interregional Road System, a highway system that connects major economic centers of the state,[8] and has been selected by the California Department of Transportation (Caltrans) as a High Emphasis Route and Focus Route from US 101 to SR 29 and SR 53 to I-80, with the designated corridor following SR 29 and SR 53 around the south side of Clear Lake.[9][10] It is also eligible for the State Scenic Highway System from SR 1 to SR 16 and SR 49 to I-80,[11] and has been designated as such for 6 miles (9.7 km) near the east end;[12] this is part of the federally designated Yuba-Donner Scenic Byway, a National Forest Scenic Byway that uses SR 20 east of SR 49.[13]

Marker along California State Route 20.

History
Donner Summit near the eastern terminus of SR 20

The east end of SR 20, from Bear Valley (just below Emigrant Gap) to Nevada City, closely follows a branch of the Truckee Route of the California Trail, first used by California-bound emigrants in 1850.[4] Later a turnpike was built here by the same company that opened the Pacific Turnpike (Culbertson Road and Bowman Lake Road between Dutch Flat and Bowman Lake) in 1864.[14]

By the end of the 1910s, a passable dirt and gravel road connected Ukiah and Nevada City via the south side of Clear Lake and Marysville. The portion between Lower Lake and Wilbur Springs was impassable in wet weather, at which times the Bartlett Springs and Bear Valley Toll-road via Upper Lake and Bartlett Springs was available for $1.50 each way or $2.50 round trip. This route generally followed the present SR 20, except around Clear Lake and between Marysville and Rough and Ready (where it used Spenceville Road). Beyond Nevada City to Emigrant Gap, the old turnpike was not passable; instead the present SR 174 was available for eastward drivers. Between Williams and Colusa, the road was paved in concrete,[15][16] as it had been added to the state highway system as part of the first (1910) bond issue, specifically as Route 15, connecting the west Sacramento Valley trunk (Route 7, now I-5) with the county seat of Colusa.[17]

This state highway was significantly extended in both directions in 1919, west to Ukiah and east to Emigrant Gap,[17] creating what was known as the Tahoe-Ukiah Highway, connecting Ukiah and Lake Tahoe in combination with Route 37 (now I-80) and Route 38 (now SR 89).[18] The law that defined the extension simply stated that it would connect "Ukiah to Tahoe City";[19] the state decided in September 1925 that it would run the highway along the north shore of Clear Lake, combining with the planned Rumsey-Lower Lake Highway (Route 50, now SR 53 and SR 16) east to Wilbur Springs.[20][21] With the completion of this segment in mid-1932, the highway was ready for heavy travel,[22] and became Sign Route 20 in 1934 as part of the initial signed state route system.[23]

In 1953, the legislature added an extension of Route 15 from US 101 at Willits (north of Ukiah) west to SR 1 near Fort Bragg.[24] This was constructed (over an existing county road[25]) and became part of Sign Route 20 prior to 1964,[26] when the Route 20 designation was legislatively adopted.[27] Subsequent improvements include the construction of the Golden Center Freeway, connecting Grass Valley with Nevada City, in the late 1960s, and a new alignment of SR 20 west from Grass Valley, bypassing Rough and Ready, in the mid-1980s.[28]

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 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).[1] 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.

CountyLocationPostmile
[1][28][29]		Exit
[30][31]		DestinationsNotes
Mendocino
MEN R0.00-44.11		Fort BraggR0.00 SR 1 – Fort Bragg, CasperWest end of SR 20
WillitsR33.16 To US 101 north / South Main StreetFormer US 101 north
​​ US 101 north – EurekaInterchange; west end of US 101 overlap; US 101 exit 568
​​West end of freeway on US 101
​R32.63[N 1]557West Road – Redwood Valley
Calpella​East end of freeway on US 101
30.83[N 1]
33.22		 US 101 south – UkiahInterchange; east end of US 101 overlap; US 101 exit 555B
​33.77Road 230 (Road 144) – Redwood ValleyInterchange; serves Redwood Valley Rancheria
​R38.05Potter Valley Road – Lake PillsburyAt-grade intersection eastbound; interchange westbound
Lake
LAK 0.00-46.48		​8.32 SR 29 – West Shore Resorts, Lakeport, Kelseyville
​31.62 SR 53 – Clearlake, Lower Lake, Middletown
Colusa
COL 0.00-R39.34		Wilbur Springs3.45 SR 16 – Rumsey, Brooks, Woodland
WilliamsT20.56
SR 20 Bus. east (E Street)
R21.85Williams (I-5 Bus., Old Highway 99W, 7th Street)Interchange; former US 99W
R22.12 I-5 – Redding, SacramentoInterchange; I-5 exit 578
T23.19
SR 20 Bus. west (Husted Road) / Freshwater Road
Colusa31.09 SR 45 north (Market Street) / 10th Street – PrincetonWest end of SR 45 overlap
​36.79 SR 45 south – GrimesEast end of SR 45 overlap
Sutter
SUT R0.00-17.06		Yuba City15.57 SR 99 – Chico, Sacramento
16.33Live Oak Boulevard, Olive StreetLive Oak Boulevard was former US 99E north
16.84Sutter StreetInterchange
Sutter–Yuba
county line		Yuba City–Marysville line​10th Street Bridge over Feather River
Yuba
YUB 0.00-21.67		Marysville​I StreetInterchange; eastbound exit and entrance
0.99 SR 70 south (E Street) / 9th Street – SacramentoWest end of SR 70 overlap; former US 99E south
1.47 SR 70 north (B Street) – OrovilleEast end of SR 70 overlap
​13.27 CR E21 (Marysville Road) – Browns Valley, Dobbins, La Porte, Collins Lake, Bullards Bar Reservoir, Brownsville
Nevada
NEV 0.00-45.66		Grass ValleyR12.16McCourtney Road, Mill StreetInterchange
R12.24 SR 49 south / Empire Street – AuburnInterchange; west end of SR 49 overlap
​West end of freeway
R12.92182A SR 174 – Colfax, Grass Valley
R13.61182BIdaho Maryland Road, East Main Street – Grass Valley
​R14.80183Brunswick Road
​R15.92185AGold Flat Road, Ridge RoadSigned as exit 185 westbound
Nevada CityR16.74185BSacramento Street – Nevada CityEastbound exit and westbound entrance
R16.99–
R17.24		186Broad Street, Coyote Street – Nevada City
​East end of freeway
R17.40 SR 49 north / Uren Street – DownievilleEast end of SR 49 overlap
​45.66 I-80 – Reno, SacramentoInterchange; east end of SR 20; I-80 exit 161
1.000 mi = 1.609 km; 1.000 km = 0.621 mi
  1. Indicates that the postmile represents the distance along US 101 rather than SR 20.
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See also
  •  California Roads portal

References
  1. California Department of Transportation. "State Truck Route List". Sacramento: California Department of Transportation. Archived from the original (XLS file) on June 30, 2015. Retrieved June 30, 2015.
  2. "Special Route Restrictions". Caltrans. Retrieved 2014-07-28.
  3. Google Maps street maps and USGS topographic maps, accessed January 2008 via ACME Mapper
  4. U.S. Forest Service, Pioneer Trail, revised May 2006
  5. "Article 2 of Chapter 2 of Division 1 of the California Streets and Highways Code". Sacramento: California Office of Legislative Counsel. Retrieved February 6, 2019.
  6. Federal Highway Administration (March 25, 2015). National Highway System: California (North) (PDF) (Map). Scale not given. Washington, DC: Federal Highway Administration. Retrieved October 19, 2017.
  7. 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.
  8. California State Legislature, CA Codes (shc:163-164.56) Archived 2009-05-01 at the Wayback Machine, accessed March 2008
  9. California Department of Transportation, High Emphasis Routes, January 2005
  10. California Department of Transportation, Focus Routes, January 2005
  11. "Article 2.5 of Chapter 2 of Division 1 of the California Streets & Highways Code". Sacramento: California Office of Legislative Counsel. Retrieved February 6, 2019.
  12. California Department of Transportation (August 2019). "Officially Designated State Scenic Highways and Historic Parkways" (XLSX). Sacramento: California Department of Transportation. Retrieved October 19, 2017.
  13. National Scenic Byways Online, Yuba-Donner Scenic Byway Archived 2008-02-14 at the Wayback Machine, accessed January 2008
  14. California Highways and Public Works: Centennial Edition, September 9, 1950, p. 64
  15. Official Automobile Blue Book, Volume Eight, 1919, pp. 146-147, 176-178, 225-226, 231
  16. Automobile Club of Southern California, Automobile Road Map of California, 1917
  17. Howe & Peters, Engineers' Report to California State Automobile Association Covering the Work of the California Highway Commission for the Period 1911–1920, pp. 11-16
  18. Ben Blow, California Highways: A Descriptive Record of Road Development by the State and by Such Counties as Have Paved Highways, 1920 (Archive.org or Google Books), pp. 104-105
  19. California State Assembly. "Senate Constitutional Amendment No. 27—Resolution to propose to the people of the State of California an amendment to the constitution of said state, by adding to article sixteen thereof a new section to be numbered two, providing for the..." Forty-third Session of the Legislature. Statutes of California (Resolution). State of California. Ch. 46 p. 1520.
  20. Oakland Tribune, Highway Commission Lays Plans for Building Lake Connection, September 6, 1925
  21. Fresno Bee, Route Follows Lake Shore, September 27, 1925
  22. Cass Kennedy, Oakland Tribune, Tahoe-Ukiah Highway Ready for Heavy Travel, March 6, 1932
  23. [Dennis, T.H. (August 1934). "State Routes Will Be Numbered and Marked with Distinctive Bear Signs". California Highways and Public Works. 11 (8): 20–21, 32. ISSN 0008-1159 – via Archive.org.
  24. California State Assembly. "An act to amend Section 315 of the Streets and Highways Code, relating to the State Highway System". 1953 Session of the Legislature. Statutes of California. State of California. Ch. 1408 p. 3002.: "Route 15 is from Route 56 near Fort Bragg to Route 37 near Emigrant Gap via Willits, Calpella, Williams and Colusa."
  25. H.M. Gousha Company, California Archived 2008-08-22 at the Wayback Machine, 1955
  26. H.M. Gousha Company, California, 1963
  27. California State Assembly. "An act to add Section 253 and Article 3 (commencing with Section 300) to Chapter 2 of Division 1 of, and to repeal Section 253 and Article 3 (commencing with Section 300) of Chapter 2 of Division 1 of, the..." 1963 Session of the Legislature. Statutes of California. State of California. Ch. 385 p. 1173.: "Route 20 is from: (a) Route 1 near Fort Bragg to Route 101 at Willits. (b) Route 101 to Route 80 near Emigrant Gap via Williams and Colusa."
  28. California Department of Transportation (July 2007). "Log of Bridges on State Highways". Sacramento: California Department of Transportation.
  29. California Department of Transportation, All Traffic Volumes on CSHS, 2005 and 2006
  30. California Department of Transportation, California Numbered Exit Uniform System, State Route 20 Freeway Interchanges, Retrieved on 2009-02-05.
  31. California Department of Transportation, California Numbered Exit Uniform System, U.S. Route 101 Freeway Interchanges, Retrieved on 2009-03-21.

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