SR 29 in VallejoA crowd watches the 4th of July parade on SR 29 in Vallejo in 2016End of SR 29 at SR 20 in Upper Lake
SR 29 begins at Interstate 80 (I-80) just north of the Carquinez Bridge in Vallejo. After running through the downtown area of Vallejo, it travels as a four-lane expressway (on some segments, five) through American Canyon to Napa. It then briefly becomes a freeway as it passes through Napa.
The expressway continues through the southern Napa Valley before terminating in Yountville. SR 29 continues as a 2-lane road through the Napa Valley cities of Oakville, Rutherford, St. Helena, and Calistoga, while also passing many of the region's notable vineyards and wineries. This portion of the highway is often heavily congested with rental cars and tour buses in spring and summer, when tourists flock to Napa Valley.
North of Calistoga, SR 29 climbs Mount Saint Helena, an extinct volcano, at the border between Napa County and Lake County. The road then heads north to Middletown and Lower Lake before going around the southern and western sides of Clear Lake, the largest natural freshwater lake completely within California. In Lakeport, SR 29 becomes a freeway as it bypasses the city. It then reverts as a two-lane highway before it terminates at Route 20 in Upper Lake.
Historically, the route between the Napa Valley and Middletown was served by the Old Bull Trail Road, built by volunteers in the 1850s, that had grades of up to 35 percent. In 1868, this was replaced by the St. Helena Toll Road, which had more manageable inclines of up to 12 percent. The State of California purchased the toll road in 1925.
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.
Southern terminus of SR 221; at-grade intersection being converted to a double roundabout interchange that is scheduled to be open for traffic in fall 2024;[10][11] SR 221 temporarily accessible as a northbound only interchange; Soscol Ferry Road accessible as a southbound only interchange
^ 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.
^"Article 2 of Chapter 2 of Division 1". California Streets and Highways Code. Sacramento: California Office of Legislative Counsel. Retrieved February 6, 2019.
^Federal Highway Administration (March 25, 2015). National Highway System: California (North)(PDF) (Map). Scale not given. Washington, DC: Federal Highway Administration. Retrieved October 18, 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.