Mount Diablo State Park

1300 N Gate Rd, Walnut Creek, CA 94598

Mount Diablo State Park is a 20,000-acre state park in the San Francisco Bay Area, in Contra Costa County. The park protects Mount Diablo, an upthrust peak just 3,849 feet (1,173 m) tall, but towering over its surroundings, offering spectacular views from its summit that can extend to Mount Lassen 181 miles north on clear days.

History

For many Native Americans, Mount Diablo is sacred and was considered by the Miwok Indians as the point of creation. At Rock City and elsewhere in the area, signs of Native American activity can be found today, with grinding holes in the stone showing were the Miwok once crushed acorns and other nuts into powder.

The mountain played a vital role in the Western United States' initial survey in 1851 when Colonel Leander Ransom chose the mountain's southern peak as his point of departure. Upon this point, subsequent surveys were located in much of California, Oregon, and Nevada.

Mountain conservation began in 1931, when the state bought land around the top, establishing a park. In the 1930s, the Civilian Conservation Corps made various improvements to the area, including roads, trails, ranger houses, maintenance facilities, campgrounds, and picnics. The CCC also designed the Summit Visitor Center using quarried stone from the mountain, and today, tourists can see shells and other fossils preserved in this natural building material.

The beacon on Mt. Diablo was turned off on December 8, 1941, the day after the attack on Pearl Harbor, to prevent enemy planes from using the light to establish their location. A ceremony was held at the visitor's center on Mt. Diablo on December 7, 1964, which included jets flying overhead and local dignitaries speaking. The object was to turn the beacon on once again. On cue, the last remaining American fleet admiral, Admiral Chester W. Nimitz, flipped the switch flipping on the light. The light has been on at night on 7 December ever since and only once a year.

In 1971 the founding of the Save Mount Diablo group started a campaign to expand the park and to protect the mountain from construction. The park has since expanded in size from 6,788 acres to around 20,000 acres. Furthermore, the park is surrounded by more than 80,000 acres that are now covered by a system of forests, parks, and open spaces extending from Suisun Bay all the way south to Interstate 580, near Livermore.

Landscape

Mount Diablo is relatively young as a geologic feature, having been formed about a million years ago. The mountain lies between converging faults in the earthquake and was created by an uplift that continues today, pushing the mountain 3-5 mm higher each year. The peak and heart of the mountain are composed of greenstone, an igneous rock that is 90-190 million years old, while the slopes of the mountain contain large deposits of sandstone, deposited in ancient seabeds and swamps and filled with fossil deposits.