Preparedness Day Bombing

The Preparedness Day Bombing was a bombing in San Francisco, California on July 22, 1916, when the city held a parade in honor of Preparedness Day, in anticipation of the United States' imminent entry into World War I. During the parade a suitcase bomb was detonated, killing ten and wounding 40 in the worst attack in San Francisco's history.

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

By mid-1916, after viewing the carnage in Europe, the United States saw itself poised on the edge of participation in World War I. Isolationism remained strong in San Francisco, not only among radicals such as the Industrial Workers of the World ("the Wobblies"), but also among mainstream labor leaders. At the same time, with the rise of Bolshevism and labor unrest, San Francisco's business community was nervous. The Chamber of Commerce organized a Law and Order Committee, despite the diminishing influence and political clout of local labor organizations. The Preparedness Day Parade was organized by the Chamber of Commerce and the anti-union conservative business establishment.

The huge Preparedness Day parade of Saturday, July 22, 1916, was a target of radicals. An unsigned antiwar pamphlet issued throughout the city in mid-July read in part, "We are going to use a little direct action on the 22nd to show that militarism can't be forced on us and our children without a violent protest." Mooney had been tipped off to threats that preceded the parade and pushed resolutions through his union, the Molders, and the San Francisco Central Labor Council and the Building Trades Council warning that provocateurs might attempt to blacken the labor movement by causing a disturbance at the parade.