White Rock Road is a twenty-eight-mile-long highway corridor which begins at the Chowchilla River in Merced County and ends at Old Highway 18 in Mariposa County near the town site of Bridgeport. The portion of White Rock Road between the Merced County and Mariposa County line to Bridgeport (via the town site of White Rock) is one of the oldest continuously used highway corridors in California. Once known as the "Mariposa River Road" the corridor was developed in the 1850s as one of the two primary highways to the mining communities of Mariposa County.
White Rock Road was bypassed in 1918 when Legislative Route Number 18 was completed between Merced and Mariposa. The corridor was for time known as Mariposa and Le Grand Road prior to the construction of Mariposa Creek Dam (formerly Mariposa River) in 1948. Following construction of the dam the roadway took the name it has now and was extended through Merced County to the Chowchilla River. Much of modern White Rock Road in Mariposa County consists of a gravel surface and is now rarely utilized as through corridor.
The Mariposa River Road can be seen connecting the Stockton-Los Angeles Road at the Mariposa County and Merced County line northeast to Bridgeport below on the 1882 Bancroft's Map of California.
Part 1; the history of White Rock Road
Mariposa County was incorporated on February 18, 1850, as one of the original counties following California becoming an American state. Mariposa County initially was by far the largest county by area in California which was centered around mining claims in the Sierra Nevada foothills. The original county seat was the now ghost town of Aqua Fria.
During the early days of Mariposa County two major highways were established between San Joaquin Valley and the major mining communities to the east of the Sierra Nevada foothills. The northern route was the now so-called "Old Toll Road" which connected Hornitos to Mount Bullion. The southernly route followed the Mariposa River (now Mariposa Creek) from the town of Bridgeport via the community of White Rock. This southern route is what is now known in modern times as "White Rock Road."
The Mariposa River Road can be seen spanning from Mariposa southwest towards what would become the Stockton-Los Angeles Road on the 1852 C.D. Gibbs Map of the Southern Mines. White Rock is shown to be known at the time as "Guadalupe" and was located north of Texas Ranch.
The Stockton-Los Angeles Road came into use after the 1853 Kern River Gold Rush began. The new highway was a replacement of the earlier El Camino Viejo. Unlike El Camino Viejo the Stockton-Los Angeles Road avoided the dense Tule Marches in San Joaquin Valley. The routing would connect it directly with the road following the Mariposa River to Bridgeport.
The Mariposa County seat would transfer to the community of Mariposa in 1854. Mariposa was centered around the Mariposa River and thusly had a direct connection with Bridgeport in addition to Mount Bullion. On April 19, 1855, Merced County would be split from a portion of western Mariposa County. The Stockton-Los Angeles Road formed the basis for much of the Merced County and Mariposa County line which can be seen on the 1857 Britton & Rey's Map of California.
During 1861 the White Rock Cemetary would be established near the namesake community along the Mariposa River Road. Said road can be seen on the 1882 Bancroft's Map of California connecting the Stockton-Los Angeles Road (labeled as Forty Mile Road) northeast to Bridgeport via Lewis. Lewis is shown to have been located a short distance south of White Rock (which doesn't appear on the map). A spur south of White Rock is shown connecting more directly south to the Stockton-Los Angeles Road at Newton's Ferry located on the Chowchilla River.
The demise of the Mariposa River Road as the primary north/south highway in Mariposa County would begin with the 1909 First State Highway Bond Act. Said act defined and extension of Legislative Route Number 18 west from Mariposa to the city of Merced. The entirety of the State Highway corridor (including the Merced River Canyon to El Portal) would be surveyed by 1913. Construction of the 38-mile State Highway corridor between Merced-Mariposa would begin during December 1915 and would be complete by May 1918. Today much of this corridor is known as "Old Highway 18" in Mariposa County and lies south of modern California State Route 140.
The history of Legislative Route Number 18 between Merced and Mariposa is preserved on a plaque found at the intersection of Old Highway 18/Yaqui Gulch Road.
The 1920 United States Geological Survey Map shows the Mariposa River Road renamed as "Mariposa and Le Grand Road." The road is shown connecting from Bridgeport to the Stockton-Los Angeles Road (shown as Old Fort Miller and Stockton Road). White Rock, White Rock Mine, White Rock School, Lewis and Dennis School are shown as major waypoints. Notably the United States Geological Survey had yet to update their Indian Gulch map to display the completed Legislative Route Number 18.
The 1935 Division of Highways Map of Mariposa County displays the entirety of Mariposa and Le Grand Road. Said road is shown to continue west into Merced County towards Le Grand as Jordan Road.
The 1954 United State Geological Survey Map of Indian Gulch is the first to display the name "White Rock Road." The corridor is shown to have been extended through Merced County south to Madera County Road 19 at the Chowchilla River. The corridor within Mariposa County had been slightly altered south of the White Rock town site when Mariposa Creek Dam was constructed in 1948.
The full extent of modern White Rock Road can be seen below.
Northbound White Rock Road can be accessed from Santa Fe Avenue in Merced County
White Rock Road branches north from Santa Fe Avenue towards Le Grand Road.
Traffic following northbound White Rock Road is required to follow a brief overlap onto Le Grand Road and make a left-hand turn to continue.
Northbound White Rock Road approaches Mariposa Creek and begins to wind through farm parcels towards the Sierra Nevada foothills.
White Rock Road crosses into Mariposa County where it once intersected the long defunct Stockton-Los Angeles Road.
Northbound White Rock Road approaches Mariposa Creek Dam and begins a brief uphill ascent.
Northbound White Rock Road jogs through the terrain and enters what was the town site of White Rock. A derelict barn serves as subtle evidence of where the community once stood.
White Rock Road begins to follow the course of Mariposa Creek and passes the site of the 1861 White Rock Cemetery.
East of the cemetery White Rock Road intersects Westfall Road. Westfall Road is the corridor shown on the 1882 Bancroft's Map in Part 1 which connected to the Stockton-Los Angeles Road at Newton's Ferry. The modern corridor continues south to Preston Road as an unpaved highway.
Traffic continuing on northbound White Rock Road is advised the paved surface ends at a one-lane bridge. A sign notifies traffic that Mariposa is fifteen miles away. Old Highway 18 is approximately ten miles to the north.
White Rock Road follows the course of Mariposa Creek and begins a somewhat steep climb into the Sierra Nevada foothills.
White Rock Road crests a ridge located at approximately 2,000 feet above sea level and faces north into the mountains of Mariposa County.
White Rock Road descends back to the course of Mariposa Creek and crosses a large stone embankment.
White Rock Road approaches a bridge which crosses Mariposa Creek.
The Mariposa Creek Bridge is a repurposed Yosemite Valley Railroad turntable. The turntable was once housed on the line at Merced Falls. The turntable was relocated to White Rock Road in 1968, flipped upside down and placed on concrete abutments to serve as a highway bridge.
The Yosemite Valley Railroad operated as a tourism to Yosemite National Park between 1907-1945. The line originated at the city of Merced and ended at El Portal in the Merced River Canyon.
White Rock Road beings to climb from Mariposa Creek and regains a worn asphalt surface. The northern terminus of the highway is located at Old Highway 18 near the site of Bridgeport.
A plaque detailing the history of Bridgeport can be found on Old Highway 18 a short distance from the terminus of White Rock Road. The community was founded in 1852 at the highway crossing near Aqua Fria Creek which was on the Fremont Land Grant site. The community reached a peak population of about 3,000 during the California Gold Rush and was once the home of the Washburn Brothers who would later construct the Wawona Road (now in Yosemite National Park). Bridgeport would finally fade when the modern alignment now used by California State Route 140 was constructed to the north.
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