Before Wall Street crashed in the 1920s, it exploded. In 1920, Morgan Bank, then the world’s biggest financial institution, was targeted by that era’s equivalent of a car bomb: a horse-drawn cart filled with dynamite. The resultant explosion killed 38 people (and, presumably, at least one horse). The brazen act of violence, and the determination to solve the crime, helped launch the career of a young investigator named J. Edgar Hoover – but the motives, and the perpetrators, pr