On September 16, 1920, an unmarked horse-drawn cart pulled up outside the J. P. Morgan bank building in lower Manhattan and detonated, killing 38 people in what was then the deadliest terrorist attack on U.
S. soil. The blast obliterated the wagon and the horse, leaving behind a chaotic scene of twisted metal, sash weights used as shrapnel, and immense destruction.
With no security footage, DNA testing, or modern forensic databases, NYPD detectives and federal agents faced an almost impossible task in identifying the owner of the cart. Their most critical breakthrough came from an unlikely source: the blast debris left behind by the horse's hooves. Investigators painstakingly recovered iron fragments from the scene and discovered a crucial clue—a unique, custom-made iron horseshoe tip designed specifically to alter the stride of a horse with an uneven gait.
Bureau of Investigation agents scoured hundreds of blacksmith shops across New York, New Jersey, and Connecticut, showing farriers the unusual shoe fragment. Eventually, a blacksmith in Manhattan recognized the distinctive handiwork, recalling that he had shod a horse matching that exact description just hours before the explosion. This forensic milestone allowed investigators to reconstruct the bomber's timeline and route through New York City.
Although the mystery was never officially solved—with primary suspicion falling on Italian anarchists—the horseshoe investigation proved to be a groundbreaking early triumph in federal criminal forensics.