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Madera County Road 420 (Thornberry Road)

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Madera County Road 420 is 4.2 mile mostly dirt surfaced cutoff between Road 223 (Teaford Saddle Road) at Teaford Saddle and California State Route 41 in Deadwood Gulch. The corridor flanks the northern ridge of the 4,433-foot-high Thornberry Mountain and was once known as Thornberry Road.
Thornberry Road first appears on the 1914 Madera County Surveyor's Map serving as a cutoff connecting Coarsegold more directly with Crane Valley (Bass Lake). The Road 420 name was assigned to the corridor in the middle of the Twentieth Century when Madera County to a numbering system. Much of the corridor remains unsurfaced into modern times due to the bulk of it being located in the boundary of Sierra National Forest.




Part 1; the history of Thornberry Road

The communities of Coarsegold and Oakhurst are two of the oldest in what is now eastern Madera County.  Coarsegold was plotted along Coarsegold Creek in 1852 whereas Fresno Flats (renamed as Oakhurst by 1912) was plotted at the Fresno River in 1858.  Both communities were located near the extensive logging interests in Crane Valley along what was then called the North Fork San Joaquin River.  

As originally configured the northern Fresno County road network did not provide Coarsegold with direct access to Crane Valley.  Travelers from Coarsegold had to take a northern route climbing from the top of Deadwood Gulch into Fresno Flats (now Madera County Road 425B).  From Fresno Flats travelers would turn east on Crane Valley Road (Now Madera County Road 426) which required ascending to the vicinity of Teaford Saddle.  

The existing road network of northern Fresno County can be seen on the 1882 Bancroft's map of California.  Northern Fresno County would split off into Madera County in 1893. 


Thornberry Road can be seen for the first time on the 1914 Madera County Surveyor's Map.  The then new roadway flanked the northern ridgeline of Thornberry Mountain and served as a cutoff from Deadwood Gulch east directly to Teaford Saddle.  The road was constructed seemingly to provide Coarsegold with far more direct access to Crane Valley and Bass Lake.  


Thornberry Road appears as a minor connector highway on the 1935 Division of Highways map of Madera County.  


During the middle of the twentieth century Madera County dropped road names in favor of a numbered grid.  Thornberry Road was subsequently reassigned as Madera County Road 420.  Road 420 can be seen below as it was displayed on the 1953 United States Geological Survey map of Bass Lake.  


Modern residential growth out of Oakhurst has seen part of Road 420 developed east of California State Route 41.  All the same much of the roadway lies within a leg of Sierra National Forest.  Road 420 east of Ceder Mountain Lane remains a dirt surfaced corridor into modern times.  



Part 2; a drive on Madera County Road 420

Westbound Road 420 begins at Teaford Saddle (elevation 3,877 feet above sea level) in Sierra National Forest at Road 223 (formerly Teaford Saddle).  There are no street blades or signage indication for traffic that Road 420 is present.  Road 420 is known to be impassable during wet weather and the lack signage is likely a deterrent for traffic using it as shortcut to Coarsegold.  



Westbound Road 420 has a partially tree obstructed vista of Oakhurst.  The entire corridor lies directly north of the 4,433 high Thornberry Mountain.  









Westbound Road 420 by Madera County standards is often in a poor state of repair for a dirt highway.  The corridor was impassable to low clearance vehicles when the photos in this blog were taken during May 2025.  Madera County workers grade the roadway during early May following the rainy season in the Sierra Nevada foothills which renders it passable to low clearance vehicles for summer months.  








Road 420 westbound emerges from Sierra National Forest and becomes paved at Cedar Mountain Lane.  



























Road 420 descends to a terminus at California State Route 41 in Deadwood Gulch.  Overhead Deadwood Peak can easily be seen.  






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