California State Route 121

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State Route 121

SR 121 highlighted in red
Route information
Maintained by Caltrans
Length33.567 mi[1] (54.021 km)
Major junctions
South end SR 37 at Sears Point
Major intersections
North end SR 128 near Lake Berryessa
CountryUnited States
CountiesSonoma, Napa
Highway system
SR 120 SR 123

State Route 121 (SR 121) is a state highway in the U.S. state of California. It runs through the Wine Country region of Sonoma and Napa counties. Its southern terminus is at State Route 37 at Sears Point, and its northern terminus is at State Route 128 near Lake Berryessa. SR 121 passes through the Carneros region of the southern Sonoma Valley and Napa Valley.

Route description

A sign on SR 37 directing drivers to SR 121

The route begins at SR 37 in Sears Point, and then runs past the Tolay Lake basin and across Tolay Creek near Infineon Raceway. As it continues northward through Sonoma County, it meets SR 116, where it then veers east. SR 121 then enters Schellville, where it begins a short overlap with SR 12. Upon leaving, it begins another overlap with SR 29, which happens to be a freeway, in Napa County. When it leaves, it continues northward and meets SR 221 in Napa. As it leaves the city, it continues northward for several miles before reaching its north end at SR 128 near Lake Berryessa.

SR 121 is part of the California Freeway and Expressway System,[2] but is not part of the National Highway System,[3] a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.[4] SR 121 is eligible to be included in the State Scenic Highway System,[5] but it is not officially designated as a scenic highway by the California Department of Transportation.[6] The California Legislature named the route Carneros Highway from its southern terminus to its junction with SR 29 in Napa, after the Carneros settlement.[7] The stretch in Sonoma County between SR 37 and SR 116 runs along Arnold Drive, and along Fremont Drive between SR 116 and the Napa County line.


The section from SR 37 to SR 29 in Napa remains virtually unchanged since its definition in 1963. The northern section, however, was slightly altered since its definition the same year due to a realignment of various other freeways.[8]

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 numbers reset at county lines; the start and end postmiles in each county are given in the county column.

SON 0.00-11.62
Sears Point0.00 SR 37 – Vallejo, NovatoSouth end of SR 121
SR 116 west (Arnold Drive) / Bonneau Road – Glen Ellen, Petaluma
SR 12 west (Broadway) – Sonoma, Boyes Hot Springs, Glen Ellen
South end of SR 12 overlap
R10.79Napa Road
NAP 0.00-22.08
R8.66[N 1]

SR 29 south / SR 12 east – American Canyon, Vallejo, Fairfield
North end of SR 12 overlap; south end of SR 29 overlap
 South end of freeway on SR 29
 North end of freeway on SR 29
R10.30[N 1]

SR 29 north / Imola Avenue west – Calistoga
Interchange; north end of SR 29 overlap; SR 29 exit 16
SR 221 south (Soscol Avenue south) / Imola Avenue east – Vallejo, Oakland
6.55Soscol Avenue north – Downtown Napa
9.40Silverado Trail, Trancas Street
16.07Wooden Valley Road – Fairfield
22.08 SR 128 – Winters, Lake Berryessa, RutherfordNorth end of SR 121
1.000 mi = 1.609 km; 1.000 km = 0.621 mi
  1. ^ a b Indicates that the postmile represents the distance along SR 29 rather than SR 121.


  1. ^ a b 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. ^ "Article 2 of Chapter 2 of Division 1". California Streets and Highways Code. Sacramento: California Office of Legislative Counsel. Retrieved February 6, 2019.
  3. ^ Federal Highway Administration (March 25, 2015). National Highway System: California (North) (PDF) (Map). Scale not given. Washington, DC: Federal Highway Administration.
  4. ^ 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.
  5. ^ "Article 2.5 of Chapter 2 of Division 1". California Streets & Highways Code. Sacramento: California Office of Legislative Counsel. Retrieved February 6, 2019.
  6. ^ California Department of Transportation (August 2019). "Officially Designated State Scenic Highways and Historic Parkways" (XLSX). Sacramento: California Department of Transportation. Retrieved September 30, 2017.
  7. ^ California Department of Transportation; California State Transportation Agency (January 2021). 2020 Named Freeways, Highways, Structures and Other Appurtenances in California (PDF). Sacramento: California Department of Transportation. pp. 76, 240. Archived from the original (PDF) on October 20, 2022. {{cite book}}: |archive-date= / |archive-url= timestamp mismatch; October 10, 2022 suggested (help)
  8. ^ Faigin, Daniel P. "California Highways:Routes 121 through 128". Retrieved 2010-04-27.
  9. ^ California Department of Transportation (April 2008). "Log of Bridges on State Highways". Sacramento: California Department of Transportation.
  10. ^ California Department of Transportation, All Traffic Volumes on CSHS, 2007

External links