The Mount Diablo watchtower was built in the 1920s, by an oil company that was operating in Concord, California. After Pearl Harbor, the light at the tower was turned off to prevent Japanese aircraft from being able to see targets on the ground, in the event their forces had been sent to the bay area.
The light tower remained unused after the end of hostilities with the Empire of Japan. In present day, the inside of the tower had the Mount Diablo Summit Museum.
The museum consists of the geologic history and an anthropology of the natives in that region.
The mountian had various names given to it by the natives and by the Spaniards.
In addition, inside of the museum has a casted price if the top of the mountain for visitors to touch.