Did the Shinn Family Have the First Gravel Quarry in California?

 First off, probably not. 

Detail From Thompson & West Alameda County no. 4

1. The Shinn family came to California in 1856.
2. The first railroad in California was either the Sacramento Valley Railroad (begun in 1855) or the Arcata and Mad River Railroad (operational in 1854). They would have needed a source for the roadbed for the tracks. Did they have a quarry or quarries?
3. The Washington Township Country Club's History (1904) says "Niles claims the first gravel pit utilized in the State, situated in the creek bottom, on the Shinn property. It is a crop that never fails, as the rains of each winter replace what has been excavated during the season. In building the new amphitheatre on the State University grounds, in Berkeley, one order was for seventy-five carloads of this gravel." Work on the railroad in Niles began in our area in 1865 and finished in 1869. Before that, there was no way to transport gravel. Often there is a nugget of truth in these rumors, so what is it?

Detail from Thompson & West Alameda Sanborn property 
Note the train coming from Niles station area
to the riverbed as in detail above.

Interesting article from the Tribune about the Hayward Fault and finding buried railroad tracks...probably from the quarry operation. 

From Oakland Tribune, November 25, 1948,