Mount Diablo Coal Field
From 1860 to 1906 this area was the largest coal mining district in California.
Five towns (Nortonville, Somersville, Stewartville, Judsonville, and West
Hartley) grew up around twelve major mines. Today the towns are gone, the buildings having been moved
to nearby communities after the mines closed. Mine openings, tailings, railroad beds, and a pioneer
cemetery are being preserved by the East Bay Regional Park District .
California Registered Historical Landmark No. 932
Plaque placed by the State Department of Parks and Recreation in
cooperation with the East Bay Regional Park District and Joaquin Murietta Chapter
No. 13, E Clampus Vitus, September 27, 1980