California State Route 175
|Defined by Streets and Highways Code § 475|
|Maintained by Caltrans|
|Length||37.89 mi (60.98 km)|
|Restrictions||No vehicles longer than 39 feet (12 m) in length between Hopland and Lakeport|
|West end||US 101 at Hopland|
|SR 29 from near Lakeport to near Kelseyville|
|East end||SR 29 at Middletown|
State Route 175 (SR 175) is a state highway in the U.S. state of California the runs through the Mayacamas Mountains, connecting U.S. Route 101 in Hopland in Mendocino County with State Route 29 in Middletown in Lake County.
SR 175 connects U.S. Route 101 at Hopland to State Route 29 near Lakeport through the Mayacamas Mountains. From there it joins SR 29 until Kelseyville, where it loops out until meeting SR 29 again at its end at Middletown. The section between Hopland and Lakeport is also known locally as the "Hopland Grade", or "Hopland Pass."
Except for the portion on SR 29, SR 175 is not 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.
Originally constructed in the early 1920s, it is one of the steepest and most difficult to drive of any California state highway. Until recently it was called the "crookedest road in California". Vehicles more than 39 feet (12 m) in length are banned from the Hopland Grade, due to its many tight hairpin turns and curves.
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 ( ). 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.
|Hopland||0.00||US 101 – Ukiah, Santa Rosa||West end of SR 175|
|SR 29 north / South Main Street – Lakeport||West end of SR 29 overlap|
|SR 29 south – Lower Lake||East end of SR 29 overlap|
|Middletown||28.04||SR 29 (Calistoga Road) / Main Street – Lower Lake, Calistoga||East end of SR 175|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi|
- Indicates that the postmile represents the distance along SR 29 rather than SR 175.
- California Department of Transportation (July 2007). "Log of Bridges on State Highways". Sacramento: California Department of Transportation.
- "Special Route Restriction History - Route 175". Caltrans. Retrieved 2018-10-13.
- Federal Highway Administration (March 25, 2015). National Highway System: California (North) (PDF) (Map). Scale not given. Washington, DC: Federal Highway Administration. Retrieved September 17, 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.
- 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.
- California Department of Transportation, All Traffic Volumes on CSHS, 2005 and 2006
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