Permanente Quarry, Limestone quarry in Santa Clara County, California
Permanente Quarry is an active limestone mining operation on the northeast slopes of Black Mountain in Santa Clara County, California. The limestone deposits formed from ancient underwater volcanoes around 100 million years ago and cover a very large area.
Mining started here in 1902 as a small operation, and Henry Kaiser bought the site in 1939 to supply cement for the construction of Shasta Dam. After that purchase, it grew into one of the largest cement producers in the region.
The limestone extracted here went into roads, dams, and airports that people across Northern California still use today. Walking or driving on much of that infrastructure means moving through something that started in this quarry.
The site is an active industrial operation, so public access is very limited and the area is not set up for casual visits. There are plans to turn parts of the land into open space and housing, which could change what is accessible in the coming years.
During World War II, this facility supplied all the cement used by the Navy across the Pacific and had around 2,000 workers on site. The demand was so high that operations ran without stopping.
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