Preparedness Day bombing

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The Preparedness Day bombing was a bombing in San Francisco, California, United States, on July 22, 1916, of a parade organised by local supporters of the Preparedness Movement which advocated American entry into World War I. During the parade a suitcase bomb was detonated, killing 10 and wounding 40 in the worst terrorist attack in San Francisco's history.

Two labor leaders, Thomas Mooney and Warren Billings, were convicted in separate trials. Mooney was sentenced to death, later commuted to life in prison, and Billings received a life sentence. Later investigations found the convictions to have been based on false testimony, and the men were released in 1939 and eventually pardoned. The identity of the bombers has never been determined.