Union Road is an approximately five-mile-long commuter highway which connects California State Routes 156 and 25 near the city of Hollister. Union Road was first developed as part of an access road which connected San Juan Bautista with Bird Creek Road (now Cienega Road) near the San Benito River. In the early 2000s the corridor of Union Road was extended east over the 1959-era San Benito River Bridge (formerly part of Cienega Road) to California State Route 25. Modern Union Road has emerged as a major commuter route for traffic departing Hollister westward to the Monterey Peninsula. The 1959-era San Benito River Bridge was recently replaced in 2025 with a modernized span designed to carry nearly 11,000 vehicles a day.
Part 1; the history of Union Road
Union Road was initially developed as a connector from Cienega Valley to San Juan Bautista (in conjunction with Bird Creek Road). The corridor in modern times now serves as a cutoff between California State Routes 156 and 25.
Cienega Valley during the period of Alta California was part of Rancho Cienega del Gabilán. The rancho had been granted by Mexican Governor Manuel Micheltorena in 1843 to Antonio Chaves. Chaves actively campaigning against U.S. forces during the Mexican-American War and fled to Mexico in 1848 as the conflict was ending.
Given Chaves was not present during the period of American Statehood in California the holdings of Rancho Cienega del Gabilán were subject to questionable claims. In 1853 the Public Land Commission would reject a claim to the rancho filed by José Yves Limantour. Limantour had claimed Chaves had sold the rancho to him but had little evidence to back it up. Thomas Larkin would make a similar claim in 1858 which was granted by the Public Land Commission shortly after he died. Following the death of Larkin, the holdings of Rancho Cienega del Gabilán would be purchased by Jesse D. Carr in 1867. Carr over the following decades would begin to subdivide his holdings.
San Benito County would split from Monterey County on February 14, 1874, largely due to the success of the New Idria Mercury Mine. The town site of Hollister was plotted in 1868 which spurred growth southward along course of the San Benito River. By 1873 the Southern Pacific Railroad would construct a spur line to Tres Pinos which served as a stage road head to New Idria via Paicines and Panoche Pass.
Development of Cienega Valley truly began on August 24, 1888, when Daniel Gilmore purchased 465 acres of land to construct a vineyard. The so-called Gilmore Colony was immediately contentious amongst Hollister locals as Gilmore intended to bring in former African American slaves from Arkansas as laborers. The first five laborers and their families would arrive in Hollister by train during February 1889.
The holdings at Gilmore Colony would expand to over 800 acres by the middle of 1889. It is likely that modern Cienega Road developed around this time to permit direct access from Hollister to Cienega Valley. Following the death of Daniel Gilmore's wife during April 1890 he would not be able to financially maintain his land holdings at Gilmore Colony. Daniel Gilmore would attempt to sell his properties numerous times to no avail and was bankrupt by the end of 1895. The workers at Gilmore Colony would ultimately relocate to Hollister.
Cienega Valley was connected to San Juan Bautista via what is now Union Road. Union Road can be seen branching from San Juan-Hollister Road east to Bird Creek Road (now Cienega Road) near the San Benito River on the 1921 United States Geological Survey map of Hollister. It isn't clear what type of bridge spanned the San Benito River in this era.
Union Road can be seen south of Hollister as a minor local roadway on the 1935 Division of Highways map of San Benito County.
The extension of Union Road to California State Route 25 saw traffic on the 1959-era San Benito River Bridge increase to 11,000 vehicles a day. The roadway became favored by commuters departing west of Hollister to work sites at the Monterey Peninsula. The 1959-era San Benito River Bridge can be seen along Union Road in June 2019 Google Street view imagery.
During 2024 San Benito County broke ground on a new bridge along Union Road over the San Bentio River intended to replace the 1959-era span. The new structure was complete on March 17, 2025, and dedication ceremony was held. Following the opening of the new San Benito River Bridge the 1959-era span was demolished.
Part 2; a drive on Union Road
Eastbound Union Road branches from California State Route 156 (San Benito-Hollister Road) near the outskirts of Hollister.
Eastbound Union Road passes through part of the Gabilan Range and intersects the western portion of Cienega Road.
Union Road crosses the San Benito River and intersects San Bentio Street. East of San Benito Street the corridor of Union Road continues a short distance to a terminus at California State Route 25.
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