Mount Diablo Beacon:

A large flashing light atop this rotunda once guided airplanes through the night skies of the Bay Area. Originally held aloft on a 75-foot tower erected by Standard Oil in 1928, it served as a crucial route-finding aid before electronic navigation. Civilian Conservation Corps workers crowned this building with a 10-million candlepower light before the outbreak of World War II. After the 1941 attack on Pearl Harbor, it was turned off amid fears it could guide the enemy in attacking the mainland. Obsolete after the war, the beacon remained dark except for an annual December 7th lighting in memorial to those who died at Pearl Harbor.

California · United States