[8] Within one minute of the explosion, William H. Remick, president of the New York Stock Exchange (NYSE), suspended trading in order to prevent a panic.

Investigators were puzzled by the number of innocent people killed and the lack of a specific target, other than buildings that suffered relatively superficial, non-structural damage.

Crews cleaned up the area overnight to allow for normal business operations, but in doing so they destroyed physical evidence that might have helped police investigators solve the crime.

[2]: 166–68 The New York assistant district attorney noted that the timing, location, and method of delivery all pointed to Wall Street and J.P. Morgan as the targets of the bomb, suggesting in turn that it was planted by radical opponents of capitalism, such as Bolsheviks, anarchists, communists, or militant socialists.

Public demands to track down the perpetrators led to an expanded role for the BOI, including the bureau's General Intelligence Division headed by J. Edgar Hoover.

[11] On September 17, the BOI released the contents of flyers found in a post office box in the Wall Street area just before the explosion.

[2]: 225–26  Investigators questioned tennis champion Edwin Fischer, who had sent warning postcards to friends, telling them to leave the area before September 16.

They found Fischer made a regular habit of issuing such warnings, and had him committed to Amityville Asylum, where he was diagnosed as insane but harmless.

[2]: 207–08  During President Warren G. Harding's administration, officials evaluated the Soviet Union and the Communist Party USA as possible masterminds of the bombing.

"[2]: 325 One Galleanist in particular, Italian anarchist Mario Buda (1884–1963), an associate of Sacco and Vanzetti and the owner of a car which led to the arrest of the latter for a separate robbery and murder, is alleged by some historians, including Paul Avrich, to be the man most likely to have planted the bomb.

[25] After leaving New York, Buda resumed the use of his real name in order to secure a passport from the Italian vice-consul, then promptly sailed for Naples.

[20] Thayer, who survived the ensuing blast that destroyed his house and injured his wife and housekeeper, moved his residence to his club for the last year and a half of his life, where he was guarded 24 hours a day.

[20] The bombing has inspired several books, notably The Day Wall Street Exploded by Beverly Gage, The Death Instinct by Jed Rubenfeld.