5. The Bombing of LaGuardia Airport in 1975

On Dec. 29, 1975 tragedy struck when a bomb went off at the LaGuardia Airport in New York City killing 11 people and seriously injuring 74 others. This attack occurred at a point in U.S. history during a period of increased terrorist activity. During that same year bombs exploded in both New York City and Washington D.C. and two attempts were made on the life of President Gerald Ford.

Even though there were suspected responsible parties, the case was never solved. Historians and investigators are of the opinion that Croatian nationalists were most likely involved. This act demonstrated the single most deadly attack on U.S. soil by a non-state actor.

4. The 1920 Wall Street Bombing

A devastating blast ripped through the Financial District of Manhattan in New York City on Sept. 16, 1920. The bombing claimed the lives of 30 individuals instantly with eight more succumbing to their wounds later. Another 143 people were severely wounded while hundreds more sustained less serious injuries. The bombing was attributed to postwar social unrest, labor struggles and anti-capitalist turmoil in the United States.

The case was never solved however, the investigators and historians believe it was the act of Italian anarchists, the Galleanists. The number of deaths that resulted from this bombing surpassed that of the bombing of the Los Angeles Times which up until that time held the title of most deadly act of terrorism occurring in the United States.

3. United Flight 23 Mid-Air Explosion in 1933

United Air Lines Boeing 247 in route from Newark, New Jersey to Oakland California exploded mid-air on Oct. 10, 1933. This flight carried three crew members and four passengers, all of which perished. The crash was proven to have been the result of an on-board explosive device.

The plane reportedly exploded at an approximate altitude of 1,000 feet, followed by a second explosion once it crashed on the ground. The tail section of the plane was blown off and found about a mile from the main wreckage.

Investigations led to the conclusion that the crash was caused by a bomb, possible containing nitroglycerin, most likely located in the baggage compartment.

This case remains unsolved with no identifiable suspects. It is considered the first proven act of air sabotage in commercial aviation.

2. The 1890 Assassination of David Hennessey

Hennessy served as the chief of police in New Orleans at a time of unrest for the city. It was riddled with political corruption and conflict. On the night of Oct. 15, 1890 he was shot by a fellow police officer in a barroom. He survived for several hours following the shooting reportedly telling those who remained close that “dagoes” were responsible for his condition. The following morning he died from complications related to his injuries.

These comments seemed to indicate that members of the Italian mafia could be responsible for the shooting. Hennessy was scheduled to testify in a trial involving two rival Italian criminal factions later that week.

Nineteen Italian and Sicilian immigrants were arrested for Hennessy’s murder, however, due to lack of evidence they were released. Protesting over the exoneration of those arrested ensued and quickly turned into a lynch mob. The city’s jail was overrun by the mob and all of the suspects were hung.

1. Preparedness Day Bombing 1916

On July 22, 1916, San Francisco was holding a parade in honor of Preparedness Day. This day signified the United States strength and preparedness to enter World War I. It was during this parade that a suitcase bomb detonated resulting in the death of 10 people and injury of 40 others.

Almost immediately the police and private detectives assigned to the case accused two radical labor leaders, Thomas Mooney and Warren Billings of the crime. Both were convicted and sentenced to death by hanging. In November of 1918 President Wilson commuted Mooney’s sentence to life in prison.  Mooney was pardoned after serving over twenty years in prison, causing the case to be reexamined. Billings was also pardoned as well.

The case of the bombing was never solved, however, three widely popular opinions of those responsible for this crime remain. First, the bombing was an act of sabotage by Germany. Second, radicalized labor unionist were responsible. And third, industrialists, as well as private detectives, planted the bomb with the purpose of smearing the antiwar movement.

This attack is consider one of the worst in San Francisco’s history.

This article originally appeared at Warrior Lodge.