On this day, September 16, in 1920, a bomb in a horse-drawn wagon exploded in front of the J.P. Morgan building on Wall Street, killing 38 and injuring 400.  At that time, the Wall Street bombing was considered one of  the deadliest terrorist attacks ever upon civilians on American soil.

It happened during the lunch rush at 12:01 p.m. in the heart of New York City’s financial district. A horse-drawn wagon pulled up to the building at 23 Wall St., and the driver quickly disappeared.   Inside of the wagon, 100 pounds of dynamite with 500 pounds of heavy, cast-iron sash weights exploded in a timer-set detonation, sending the slugs tearing through the air.  The horse and wagon were blasted into small fragments.

The Justice Department's Bureau of Investigation (BOI) did not immediately conclude that the bomb was an act of terrorism.  Investigators were puzzled by the number of innocent people killed and the lack of a specific target.   Exploring the possibility of an accident, police initially contacted businesses that sold and transported explosives.  By 3:30 p.m. on the same day of the bombing, the board of governors of the New York Stock Exchange met and decided to open for business the next day.  Crews cleaned up the area overnight to allow for normal business operations the next day, but in doing so they destroyed physical evidence that might have helped law enforcement investigators solve the crime.

Investigators soon learned that before the bomb exploded, fliers had been found at a post office box near Wall Street threatening retribution for the recent murder indictments of anarchist Nicola Sacco and Bartolomeo Vanzetti.  On September 17, the BOI released the contents of the flyers.  Printed in red ink on white paper, they said: "Remember, we will not tolerate any longer. Free the political prisoners, or it will be sure death for all of you." At the bottom was: "American Anarchist Fighters.  This led investigators to suspect that Anarchists — particularly the followers of Italian anarchist Luigi Galleani — were involved in the bombing.  Anarchists had been linked to several deadly bombings and even one mass poisoning during that time period.

The bombing stimulated renewed efforts by law enforcement and federal investigators to track the activities and movements of radicals.  Public demands to track down the perpetrators led to an expanded role for the U.S. Justice Department's Bureau of Investigation (BOI) (the forerunner of the Federal Bureau of Investigation), including the General Intelligence Division of the BOI headed by J. Edgar Hoover.

The Bureau of Investigation and local law enforcement investigated the case for years without success. Occasional arrests garnered headlines but each time they failed to support indictments.  Most of the investigations initially focused on anarchists and communists.   During President Warren G. Harding's administration, officials evaluated the Soviets as possible masterminds of the bombing and then the Communist Party USA.   In 1944, the Federal Bureau of Investigation, successor to the BOI, investigated the bombing again, but no arrests were ever made for that horrific crime committed on September 16, 1920.