It was an unorthodox way of delivering a bomb, and no one knew the danger that was carried on a horse-drawn wagon as it was pulled along busy Wall Street. In the wagon was 100 pounds of dynamite surrounded by 500 pounds of sash weights, which are heavy cast-iron weights used to counter-balance windows that slide open. The dynamite exploded at noon and sent the heavy shrapnel flying into the lunchtime crowd outside the financial buildings along Wall Street.

The attack is still unsolved, but historians believe it was carried out by an Italian anarchist group. The sheer cruelty of the bombing, which seemed to have no intended target and killed a random assortment of innocent people who were nearby, made it difficult to even theorize what the intent of the bombers had been. The federal Bureau of Investigation did find flyers with vague threats stuffed in nearby mailboxes, but they did not directly reference the bombing.

It became the worst single loss of life in the city since the Triangle Shirtwaist factory fire from nine years earlier in 1911.

Today, you can still see damage from the blast at 23 Wall Street, where part of the stone wall has been preserved showing the chips in the stone from the projectiles in the explosion.