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.
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