In 1892 Contra Costa County named Black Diamond Way, and maintained it as a road until 1982. (Locally it was also known as "Nortonville Road".) Black Diamond Way became part of Black Diamond Mt. Diablo Regional Trail in 1985.

Black Diamond District coal mines operated from 1861 until circa 1900. Between 1867 and 1883 they produced over 100,000 tons annually. Coal was hauled to river landings by teams and rail.

Miners and families from Mt. Diablo coalfield towns crossed Mt. Diablo Creek for supplies, services, and recreation. Inns and saloons outnumbered other establishments.

The City of Clayton dedicated Black Diamond Plaza on October 28, 2000.

Clayton Historical Society 2005

Marker is at the intersection of Marsh Creek Road and Main Street, on the right on Marsh Creek Road.

Courtesy hmdb.org

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