The Unsolved 1920 Wall Street Bombing
A horse-drawn wagon loaded with explosives detonated in the heart of New York City in 1920, killing 38 people. Despite the scale of the carnage, the bombers were never caught or officially identified.
At noon on a busy Thursday, a carriage carrying dynamite and heavy iron sash weights exploded, devastating the financial district. The blast shattered windows blocks away and sent thousands of workers fleeing in panic. Investigators suspected political radicals were behind the attack, but no group ever claimed responsibility. The heavy shrapnel left deep, permanent scars on the stone exterior of the J.P. Morgan building that remain visible today.
Source: Wall Street bombing