The Black Tom explosion was an act of arson by field agents of the Office of Naval Intelligence of the German Empire, to destroy U.S.-made munitions that were about to be shipped to the Allies during World War I.

By 1880, the island was transformed into a 25-acre (10 ha) promontory,[9] and a causeway and railroad had been built to connect it with the mainland to use as a shipping depot.

A 1 mi (1.6 km)-long pier on the island housed a depot and warehouses for the National Dock and Storage Company.

[13] Jersey City's Commissioner of Public Safety, Frank Hague, later said he had been told the barge was "tied up at Black Tom to avoid a twenty-five dollar charge".

[16] The explosion created a detonation wave that traveled at 24,000 feet per second (7,300 m/s) with enough force to lift firefighters out of their boots and into the air.

[28] Von Rintelen used these resources to make generous cash bribes, one of which was notably given to Michael Kristoff in exchange for access to the pier.

[28] German intelligence operatives Kurt Jahnke and Lothar Witzke were then suspected, and are still judged as responsible legally.

[35][36] It is also believed that Michael Kristoff, a 23-year-old Austrian immigrant who had served in the U.S. Army, was responsible for planting and initiating the incendiary devices that caused the explosions.

[38][39] Irish socialist and labour union leader James Larkin asserted that he had not participated with sabotage, but admitted to having encouraged work stoppages and strike actions in munitions factories, in an affidavit to McCloy in 1934.

[40][41] The United States did not have an established national intelligence service, other than diplomats and a few military and naval attaches, making the investigation difficult.

Without a formal intelligence service, the United States only had rudimentary communications security and no federal laws forbidding espionage or sabotage except during wartime,[4] making the associations with the saboteurs and accomplices almost impossible to track.

[citation needed] This attack was one of many during the German sabotage campaign against the neutral United States, and it is notable for its contribution to the shift of public opinion against Germany, which eventually resulted in American approval for participating with World War I.

[4] The Russian government[42] sued the Lehigh Valley Railroad Company operating the Black Tom Terminal on grounds that lax security (there was no entrance gate; the territory was unlit)[43] permitted the loss of their ammunition and argued that due to the failure to deliver them the manufacturer was obliged by the contract to replace them.

[13] After the war, the Lehigh Valley Railroad, advised by John J. McCloy, sought damages against Germany by the Treaty of Berlin from the German-American Mixed Claims Commission.

A military court at Fort Sam Houston found him guilty of espionage and sentenced him to death by hanging.

In September 1923, Witzke, as a result of heroic conduct in prison and pressure for his release by the Weimar Republic, was pardoned by President Calvin Coolidge, and deported to Germany.

[citation needed] Kristoff was arrested by the Jersey City police on suspicion of involvement in the blast, but later released due to a lack of evidence.

President Franklin D. Roosevelt used the Black Tom explosion as part of his rationale for the internment of Japanese Americans after the attack on Pearl Harbor in 1941.

[53] In an interview with Jules Witcover, McCloy noted that as assistant secretary of the navy for President Wilson, Roosevelt "knew all about Black Tom".

[4] Landfill projects later made Black Tom Island part of the mainland, and it was incorporated into Liberty State Park.

[29] The former Black Tom Island is at the end of Morris Pesin Drive in the southeastern corner of the park, where a plaque marks the spot of the explosion.

On July 30, 1916 the Black Tom munitions depot exploded rocking New York Harbor and sending residents tumbling from their beds.