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From the Contra Costa County Historical Society…

From the Contra Costa County Historical Society…

A History Note: The Beacon

Every December 7thsince 1964, the beacon light on the top of Mount Diablo is lit. There is a ceremony attended by the remaining survivors of the Japanese attack on Pearl Harbor in 1941 and the sons and daughters of the survivors.

The aviation beacon began its existence on a 75-foot steel tower. Below the beacon, outlined in flashing neon lights, were the 12-foot high letters “S” and “D,” standing for Standard Diablo. The beacon was one of 65 erected in California to guide airplanes at night.  This was a joint effort of the US Department of Commerce and Standard Oil, which produced aviation fuel at its Richmond refinery. The beacon revolved six times a minute and could be seen on a clear night for 100 to 150 miles. On April 15, 1928, Charles Lindberg pressed a telegraph key in Denver that carried the signal to bring the beacon to life.

In a collection of Professor Norris Pope’s Research Projects that is part of the CCCHS collections, student Harris Hudson reported in June 1955, ”When the combination beacon and searchlight sent out its rays on Clayton … no longer [were] we a deserted village, progress is ours.”

In 1931, a wildfire on Mt. Diablo threatened the beacon.  Standard Oil sent emergency equipment to restore power so that the beacon could continue to operate.   In June of 1939, the tower was dismantled so that the WPA could build the stone building that now houses a museum and visitor center. The summit is inside the building. A brass monument marks the axis of the first geodetic survey of California in 1851. In 1941, the beacon was moved to the apex of the observation tower to continue serving as a signal for planes at night. On December 8, 1941, the beacon was extinguished as part of the West Coast Blackout. It was feared that it could be used by our enemies to attack the Bay Area.    

 At the end of World War II, advances in radar and navigational equipment made the beacon obsolete, and it remained dark until Admiral Chested Nimitz woke it in 1964. He suggested that the beacon be illuminated every December 7thto remember those who had served and given their lives at Pearl Harbor. On December 7th, the beacon is lit at sunset and shines all night on this one night of the year.

A History Note is presented by the Contra Costa County Historical Society’s History Center, 724 Escobar St., Martinez. Open hours: Tuesdays, Wednesdays, and Thursdays, from 9am - 4pm, and third Saturdays, from 10am – 2pm. Check out the website at