State Route 174 begins at exit 135 of I-80 in Colfax. Immediately after crossing I-80, the route turns right on Auburn Street and right again on Central Street, which bypasses downtown; a business route follows Auburn Street, Grass Valley Street, and Main Street through downtown.[4] SR 174 follows the old Lincoln Highway (US 40) north out of downtown to Rollins Lake Road, where the present state highway turns northwest along the Colfax Highway. It then crosses the Bear River from Placer County into Nevada County on a 1987[5] bridge, with the old 1924 bridge preserved for non-motorized traffic. The land flattens out as SR 174 curves north and west through the Empire Mine State Historic Park into Grass Valley. Turning west on Colfax Avenue, the state highway passes under the SR 20/SR 49freeway before ending just beyond at Auburn Street,[1] the former surface routing of SR 49.[6]
Local residents created the Colfax Highway Association in 1967 at the Peardale firehouse, about halfway between the two ends, in order to preserve the rural nature of the road.[16] When the 21-foot (6.5 m) wide 1924 concrete arch bridge that took SR 174 across the Bear River on the county line was set for replacement in the late 1980s, the group successfully lobbied to preserve it for non-motorized traffic.[17] The association also pushed for Nevada County's Gold Country Stagebus service to add a route along the highway to Colfax, which was agreed to in late 1998[18] and still runs as Route 12, connecting downtown Grass Valley with Colfax's Amtrak station.[4] After a request by Nevada County in 1988, the state legislature designated the part of SR 174 in unincorporated Nevada County (between the county line and the Grass Valley city limits) as eligible for the State Scenic Highway System in 1991.[19] In 1999, the Colfax Highway Association attempted to get the route officially declared a State Scenic Highway. They argued that the designation would "protect the scenic character and rural flavor of the highway". A newly formed group, Concerned Citizens for 174, opposed the designation because it would restrict the property rights of residents along the highway, for instance requiring them to use "natural colors".[20] The opposition was successful,[3] and SR 174 remains eligible for State Scenic Highway status but is not a State Scenic Highway.[10]
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.
^ abcdCalifornia 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.
^Sacramento Bee, Scenic Highway Concept Spurs Alarm, March 25, 1999, p. N1
^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.
^Sacramento Bee, Highway Boosters Stay Ahead of Curve, August 17, 1997, p. N1
^Sacramento Bee, Slated for Razing, Span Gets Reprieve, January 14, 1987, p. B1
^Sacramento Bee, Bus Route to Penetrate Foothills' Last Transitless Corridor, December 10, 1998, p. N1
^California State Assembly. "An act...relating to highways". 1991–1992 Session of the Legislature. Statutes of California. State of California. Ch. 775 p. 3483.
^Sacramento Bee, Scenic Highway Concept Spurs Alarm, March 25, 1999, p. N1