The Preparedness Day Bombing and the Mooney Case
At 2:06 p.m. on 22 July 1916, a suitcase bomb exploded beside San Francisco's enormous Preparedness Day parade, killing ten people and wounding about forty. Labor activists Thomas Mooney and Warren K. Billings were convicted amid false testimony and intense political pressure. Both were pardoned in 1939; the person who planted the bomb has never been reliably identified.
What existed before
The First World War divided San Francisco between business and civic groups advocating military preparedness and labor or antiwar groups opposing militarism. The 22 July parade brought tens of thousands of marchers onto Market Street in a city already marked by bitter conflict between employers and organized labor.
Trigger and cause
A bomb concealed in a suitcase detonated near Steuart and Market Streets about half an hour after the procession began. The crowded curb became a mass-casualty scene. The blast did not itself establish who built, placed, or directed the device.
Aftermath
Police arrested Mooney, Billings, Rena Mooney, and others associated with radical labor. Mooney and Billings were convicted, but contradictory evidence, perjured witnesses, and prosecutorial conduct made the case an international cause. President Woodrow Wilson's Mediation Commission found no clear evidence of Mooney's guilt.
Why it matters
The bombing joins two histories that should not be collapsed into one: ten people were killed by an unresolved act of violence, and other people were then subjected to a deeply unreliable prosecution. A responsible account preserves both harms.
Uncertainty note
The blast's time, location, and casualties are well documented. The bomber's identity is not. This file does not transfer suspicion from the discredited Mooney and Billings cases to any alternative person for whom the historical record is also inconclusive.