Wall Street bombing
The 1920 Wall Street Bombing occurred on September 16th in which the financial district of Manhattan was bombed. The resulting mayhem led to the deaths of 38 people, with another 143 being seriously injured. The bombing was never solved, but it is believed that the bombing was carried out by an anarchist group of Galleanists who frequently protested against capitalism.
23 Wall Street still has some visible pockmarks on the wall from that attack.