Preparedness Day Parade, July 22, 1916. During a parade along Market Street to encourage Americans to participate in World War l, a bomb placed in a suitcase at the Southwest corner of Market & Steuart Streets explodes killing ten people in the worst terrorist attack in San Francisco to date. Here, a crowd gathers in confusion after the blast, Some of the victims can be seen covered in sheets at the right near the bottom of the billboards. The crime was never solved. The bomb detonated just beyond the front of the white van at the right in the modern picture.