California Historic Landmarks

Mount Diablo Coal Field

Site Information

The Greathouse Portal is the entrance to the underground visitor center.
site photo
Landmark Number: 932
Location: Black Diamond Mines Regional Preserve, South End of Sommersville Road, Antioch, Contra Costa County
Marker Plaque: Official State Plaque
Admission: Charge for parking on weekends and holidays.


From the official marker plaque:

From 1860 to 1906, this area was the largest coal mining district in California. Five towns (Nortonville, Sommersville, Stewarville, 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.


Official state marker plaque just south of the parking lot at the south end of Sommersville Road.
Plaque detail.
Rose Hill Cemetery.
Tailings piles (waste material excavated from the mine) near the Greathouse Portal.



Location and Vicinity Map

Detail Map

View larger map on OpenStreetMap or Google Maps

Home Sites Visited in Contra Costa County