The Preparedness Day Parade, organized by the San Francisco Chamber of Commerce and local businesses, took place on July 22, 1916 to advocate the United States’ entry into World War I^[1]. At the time, the majority of the City (local labor unions in particular) were against going to war because they believed the Parade was sponsored by those who would profit from United States participation.

It was to be the largest parade ever held in the City, with 51,329 participants that included 2,134 organizations and 52 bands. Weeks before the Parade, an anonymously authored pamphlet began circulating that read in part, “We are going to use a little direct action on the 22^nd to show that militarism can’t be forced on us and our children without violent protest.”

A half an hour into the projected 3.5 hour Parade, a suitcase bomb detonated at the corner of Market and Steuart across from the Ferry Building^[2], killing 10 and wounding 40. It is still considered the worst terrorist attack in San Francisco history.

The District Attorney, who is believed to have had anti-union sentiments, worked with the Chamber of Commerce to identify “troublemakers with radical views” from previous strikes. Two radical labor leaders, Thomas Mooney and his assistant Warren Billings, were immediately arrested. Both had experience with explosives: Mooney had been arrested but not convicted for conspiring to dynamite power lines during a 1913 PG&E strike, and Billings had been previously convicted for carrying dynamite onto a passenger train. Both men were quickly convicted and sentenced after being held for six days without legal representation. The conviction was so quick and controversial that President Woodrow Wilson set up a Mediation Commission on the matter. The Commission found no clear evidence of guilt, and Mooney and Billings’ sentences were commuted to life imprisonment. In 1939 it was discovered that the key witness who testified to seeing Mooney and Billings drive up in a car and place the suitcase on the street wasn’t even in the City on the day of the Parade. Mooney and Billings were eventually both pardoned by Governor Culbert Olsen and released. The real bomber was never identified or apprehended. 

^[1] World War I: https://thesanfranciscophoenix.com/?p=4079

^[2] Ferry Building: https://thesanfranciscophoenix.com/?p=5219