Diana Princess of Wales at Luanda Airport, Angola, at the start of her four-day visit to the Red Cross Projects in Angola in 1997, the year she ultimately died.

Major conspiracy theories of the last century and the stories behind them

Written by:
August 21, 2020
Tim Graham Photo Library via Getty Images

Major conspiracy theories of the last century and the stories behind them

In this fast-paced, rapidly changing media world, people have access to more information than ever before about virtually everything. But the sometimes-overwhelming amount of available data has led many people to be suspicious of what they hear, coming to their own unfounded conclusions. 

In recent years, we've seen a new conspiracy theory enter the mainstream: QAnon, which started on the internet in 2017, espouses a convoluted and sensational set of theories centered around the belief of the existence of a global cabal of child-abusing Satanists—and it only gets more outlandish from there. Its violent rhetoric has already spilled offline, causing the FBI to label it a potential domestic terrorist threat. Previously operating in the fringes of the internet, QAnon gained ground in more traditional spaces.

It may be the latest conspiracy theory to gain traction, but QAnon follows a long lineage of such events—it even incorporates previous theories, tentacle-like, into its orbit. Here, Stacker takes a look at some of the most popular, and sometimes notorious, conspiracy theories of the past century. Stacker does not include information that turned out to be true, such as the CIA mind-control project MK-Ultra. And the team has done its best to respect people who believed these theories based on their eras.

Oftentimes, conspiracy theories are simply posited guesses that turn out to be demonstrably false. But they also often tell a society something about the time and place in which they originated. When people don't understand something, they tend to use their imaginations to come up with explanations that defy reality but provide them with some degree of comfort. And other times, alternative answers are hard to come by—which is why some conspiracy theories have endured the test of time without any reasonable alternative explanation.

Read on to learn about the stories behind major conspiracy theories of the last century. 

You may also like: Weird, wild UFO sightings from throughout history

Lizard people rule the world

The idea that lizard people posing as humans run the world allegedly originated with author and former BBC sports reporter David Icke in the late 1990s. Apparently, having red hair and unexplained scars can implicate you as a lizard person. Clearly, none of this is true—although plenty of YouTube videos claim otherwise.


Is Mars' face a sign of alien life?

The year 1976 gave humanity fantastic new technology for checking out space—and a mysterious face on Mars. Some people screamed aliens at first. But NASA confirmed that it's just a hill, and future space photographs confirmed this was, indeed, the case.


Philadelphia Experiment

In 1943, the U.S. government allegedly conducted an experiment to see if it could render a war ship invisible. This conspiracy, known as the Philadelphia Experiment, in which the Navy purportedly teleported a destroyer escort from Philadelphia to Norfolk, Va., was officially declared a hoax, but it hasn't stopped influencing art pieces about it—most recently the internet horror series "Interface."


Ebola was created in a lab

This conspiracy theory persisted into the 2010s, and may still exist in some remote areas. As the Ebola virus spread in Africa at alarming rates, a conspiracy emerged that the virus was intentionally created in a lab. This was not the only conspiracy theory surrounding the deadly virus—another involved a particularly evil snake. One study found that Ebola likely came from one person.


Atlantis is real, but where is it?

People have wondered about the location of the legendary lost city of Atlantis for generations. The latest theories suggest Morocco as one possibility and Cuba as another candidate, based on landmarks described in the writings of Plato. But the search continues.


Bilderberg Meeting

The Bilderberg Meeting, a secretive gathering of diplomats and generally important people from around the world, is real. Conspiracy theories about it have centered around what exactly goes on during those meetings. The Bavarian Illuminati come up a fair amount of the time in relation to the gathering.


Shroud of Turin

In the 1980s, a conspiracy around the mysterious Shroud of Turin was finally debunked. The religious object was determined not to be Jesus's death shroud. Radiocarbon dating placed the shroud as being from the Middle Ages.


Black helicopters

Ever see a black helicopter flying overhead? Conspiracy theorists have been toying with this symbol of supposed government secrecy and abuse for decades. The truth is that many government and law enforcement agencies, including the Drug Enforcement Administration, the FBI and U.S. marshals, use black helicopters in their work.

Nazi Escape Submarine

Recently debunked, there was a deep conspiracy that a submarine was shipping escaped Nazis to South America. Things weren't helped when a vague FBI document about the matter was released in the 1950s. But in 2018, the submarine was discovered to have been sunk off the coast of Denmark.


Varig Cargo Flight 967

Varig Flight 967 took off from Tokyo in 1973 and was never seen again. The conspiracy around potential foul play arose because the plane was transporting over 50 valuable paintings. But neither the plane, nor proof of a wreck, has been found.


Was Ronaldo drugged?

The 1998 FIFA World Cup Final sparked a huge controversy around Brazilian soccer player Ronaldo, who suffered what is believed to have been an epileptic fit the night before the game. But his uncharacteristically weak performance, which cost Brazil the World Cup, sparked rumors that he had been poisoned.


Who Killed Dag Hammarskjöld?

Dag Hammarskjöld was a United Nations diplomat who was set to negotiate peace in a particularly rich area of the Congo in 1961 when he died under mysterious circumstances. His anti-colonization stance led many to believe that his death was engineered by his political opponents. To date, there's been no proof of that theory.


Who killed JFK?

Conspiracies around who killed President John F. Kennedy in 1963, and whether it was a conspiracy, possibly involving the Soviet Union, swirled after his assassination and continue to this day. They were so numerous that the Warren Commission was formed in 1964 to investigate. It concluded that Lee Harvey Oswald was the lone assassin, but many, including historians and those in the CIA, have expressed doubt about this conclusion.


Elvis is not really dead

Some diehard Elvis fans still refuse to believe that the King of Rock 'n' Roll really died in 1977, and alleged sightings of him are routinely reported. But none of the reported sightings have been determined to be true.


We're being controlled by chemtrails

Government planes are not dispersing chemicals into the sky to control the populace. This conspiracy was debunked—it's condensation from jet engines.


Sharm El Sheikh shark attacks

A series of shark attacks in Egypt led some to wonder what was drawing so many of the creatures to a popular Red Sea resort. Though some suspected enemies of the government, it was eventually concluded that dead sheep thrown overboard into the Red Sea likely had enticed the voracious predators.


Red Scare

The early 1900s were plagued by suspicions of an imminent Communist uprising within America, known as the Red Scare, and there was a second wave in the 1950s, prompting the notorious U.S. Senate hearings led by Joseph McCarthy of Wisconsin. While the Senate eventually censured McCarthy for his conduct, there was some evidence that Communist members or agents had infiltrated some levels of government.


Torn-jean messages

In 2017, a Turkish newspaper wrote that enemies of the country were covertly signaling each other through holes in denim jeans. The holes allegedly correlated to messages that the agents used to signal to each other. The notion remains unproven and no one has been arrested as being a torn-jean messenger.


Who Bombed the Moscow apartments?

In 1999, an apartment building in Moscow was bombed in what many people considered to be a terrorist act. Dozens were killed and scores were injured, and those associated with the bombing were sentenced to life. But questions surrounding their confessions in the bombing and the timing of Vladimir Putin's rise to power left many wondering if there is more to the story.

Centralia's coal

The story of an eternally burning fire in Centralia, Penn., is well known. But there was a companion conspiracy that the U.S. government wanted to buy the city's rich coal reserves—and set the fire when the sale was denied. This has since been dismissed as a rumor to explain the freakish event.


Was Jack the Ripper a royal?

Suspects in the late-1800s case of Jack the Ripper in London ranged from a barber to the sex-worker serial killings being a Freemason plot. By far the most extreme theory was that Prince Albert Victor was the perpetrator. But since no one was ever caught, the mystery—and accompanying theories—linger to this day.


Princess Diana's death was planned

The car-crash death of Princess Diana of Wales rocked the world. Many wondered if what happened to the "people's princess" was planned by the royal family in retaliation for her divorce from Prince Charles and her continuing popularity. An investigation ruled out this theory, though it has not stopped many people from wondering what happened to this day.


U.S. moon landing was a fake

Murky photos and general suspicion has led some people to conclude that the United States faked the first manned moon landing in 1969. A fake interview with film director Stanley Kubrick added fodder to the notion. Various reports and investigations have addressed the truth about traveling to the moon. Yes, U.S. astronauts did, in fact, land on the moon.


The Illuminati rule everything

Though the Illuminati were a real secret society of intellectuals in the 1700s, the Illuminati as a conspiracy theory actually developed in the 1960s through the creativity of the counterculture. They're not an all-powerful society in real life—just friends playing pranks on each other whose creative exercises were taken too seriously.


Who took Shergar?

Horse-racing fans know the legend of Shergar, the Irish champion racehorse of the early 1980s that was allegedly taken at gunpoint by people with "guns and balaclavas." Was it the Mafia or petty thieves? Rumors persist that the Irish Republican Army was to blame, but the mystery remains unsolved.


Earth is flat

Although the notion that Earth is flat has been around since ancient times, modern versions of a flat-earth conspiracy gained traction in the 1800s, proposed by religious and non-religious people alike. This conspiracy theory has been debunked many times.


9/11 could have been prevented

The trauma of the 9/11 attacks shook America, and some people wondered how U.S. surveillance could not possibly have known that such an attack was imminent or that the response was not appropriate or swift enough. But according to reports, proper protocol was followed that day.


Jesus's descendants

A popular biblical conspiracy theory follows that Jesus Christ married Mary Magdalene and created a bloodline that can be traced to today. The conspiracy was made famous by "The Da Vinci Code," but can be traced back to the 1980s to a book called "The Holy Blood and the Holy Grail." But there's no substantial evidence for this conspiracy other than some biblical passages that can also be used for the opposite argument. Unless DNA evidence is produced, this conspiracy may just have to linger in the "what if?" category.


Denver International Airport was built for occult practices

The odd symbols around Denver International Airport caused many to wonder if it is, in fact, a hub of mystical intrigue. The airport has attributed the notion to misinformation circulating on the internet. But recently, officials have embraced the interest through conspiracy-themed ads and art.


Who's Prince Harry's father?

The paternity of England's Prince Harry has been questioned ever since it was revealed that Princess Diana had an affair with former army captain James Hewitt. He has ginger hair like the prince, but Hewitt has noted that he did not begin dating Princess Diana until after Prince Harry was born.


Was Canberra designed for cult activity?

The 1900s design of Australia's capital city Canberra does look a bit mystical from the air, with all its interesting angles and shapes. But the architects were more "spiritual" than cultish and did not intend to summon the dark side. They also brought their talents to other works, such as the Capital Theatre.


Finland isn't real

The conspiracy theory that Finland isn't actually real started as a joke that eventually went too far. This theory may have attracted true followers, but the country's population of more than 5 million people can assure conspiracy theorists otherwise.


Coffee at Tim Hortons is addictive

Probably starting as a joke, Tim Hortons coffee was rumored temporarily to contain the addictive substance nicotine in order to hook customers. But the Canadian Food Inspection Agency dispelled the rumor. Technically speaking, however, caffeine in coffee is a central nervous system stimulant that can lead to mild physical addiction.


Who killed the Grasberg mine workers?

Indonesia contains the world's largest gold mine, around which much violence, including deaths, took place in 2009. Rumors swirled that the military was to blame, or corporate mercenaries looking to silence protesters concerned about American ownership of the mine. The case remains unsettled, but the mine has since changed ownership and is in the hands of Indonesians.


Canada's becoming more French

A 1977 book called "Bilingual Today, French Tomorrow," according to Canadian conspirators, is all part of a scheme to make French the country's official language. Canada's most-spoken languages still are English and French. This conspiracy theory belies a long-running prejudice against French speakers in Canada.


J.K. Rowling is an actress

One of the wackiest modern book conspiracy theories comes from Norway, where a filmmaker alleges that author J.K. Rowling is many people, not one person. The woman we see in interviews is really just an actress, and the "Harry Potter" books were written by many people, according to the filmmaker. There has been no official word from Rowling herself, but her Norwegian publisher denied the claims.


Marilyn Monroe's death was political

The untimely death in 1962 of actress Marilyn Monroe at age 36 has been fraught with conspiracies, the most notable being that she was murdered because of her connections to and knowledge of the Kennedy family. The FBI also was accused of murdering Monroe, but the case remains closed, with Monroe's official cause of death listed as "acute barbiturate poisoning."


Branwell Brontë wrote 'Wuthering Heights'

An author in 2014 announced he was launching an investigation to prove that Emily Brontë's brother, Branwell, was the true author of "Wuthering Heights." But the conspiracy is largely considered an attempt to erase a woman's work. Fans have compared themes of Emily's writing against the novel, arguing that only she could have written it.


KGB killed Albert Camus

In the 1960s, the death of writer and philosopher Albert Camus was suspected to be orchestrated by the KGB because of the author's criticism of the Soviet Union. Writings from the time suggest his death was due to sabotage, the only reason the freak car accident that killed him could have happened. But Camus's biographer disagrees, saying that he encountered no evidence of Soviet sabotage in researching his book.


Amelia Earhart died in a Japanese jail

Multiple conspiracies exist around the death of trailblazing pilot Amelia Earhart, but the most recent one emerged in 2017, alleging that Earhart actually died after being rescued in a territory controlled by the Japanese. This conspiracy was debunked by an expert who asserted that a purported photo of Earhart could not be her, and the prevailing theory remains that Earhart died as a castaway on Kiribati's Nikumaroro island.


Pan Am Flight 103 was sabotaged

After the 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland, two passengers from Libya were indicted on the charge of bombing the plane intentionally. It was a highly charged political time when Libyan leader Moammar Gadhafi was considered an enemy of many countries, including the United States. But the trial and evidence became fraught with conspiracy itself, and despite the convictions, many still believe the case is not fully solved.


China built a mockup of Washington D.C.

Is China testing weapons against fake versions of American cities? This conspiracy was debunked in 2011 by one expert, who said that the unusual structures and patterns in the Gobi desert were almost certainly being used by the Chinese to calibrate its spy satellites.


Schapelle Corby was set up

Conspiracy theorists had a field day when Australian Schapelle Corby was arrested in Bali in 2004 after a little over 9 pounds of cannabis was found in her bodyboard bag. She maintained she had no idea how it got there. Conspirators say she was a pawn in a smuggling ring of baggage handlers allegedly covered up by the government to conceal airport crime rates. Whether or not it's true, Corby served her time in prison and is now reportedly looking to live a quiet life.


Natalie Wood was murdered

Actress Natalie Wood's body was recovered a mile away from a yacht near Catalina Island in 1981, and conspiracies arose that her death was not by drowning, but murder. Suspicions were fueled by bruises and a gash on her body, the fact that Wood, her husband actor Robert Wagner, and yacht guest actor Christopher Walken had argued, and that Wood had a well-known fear of water. Her death was reclassified as "suspicious" in 2018.


Lindbergh baby is alive

The case of the 1932 kidnapping of Charles Lindbergh Jr. ended with the execution of a man who claimed he was innocent until the end. Authors and lawyers have suggested that the evidence against Bruno Richard Hauptmann was fake or coerced, and in 2010 a man in Santa Cruz, Calif., claimed he was Lindbergh's son. But so far, there's been no proof of his assertions.


Nazis set the Reichstag on fire

The Nazi party's rise to power in Germany has been tied to a mysterious fire of the political building known as the Reichstag. A communist was tried and executed for the 1933 fire at the German parliament, but conspirators say that the Nazis themselves may have been responsible as a way for Adolph Hitler to seize power. A 1981 West Berlin court ruling suggested that the man prosecuted may have been wronged—but doesn't go any further.


Business Plot was real

Smedley Butler was purportedly an ordinary soldier who brought down a group of wealthy billionaires seeking to overthrow the government in the 1930s. But did he? It's hard to say; Sources suggest the plot had some truth to it, but no one was prosecuted and the plot has mainly been relegated to conspiracy circles. Those who believe the rumors say the scheme targeted the Roosevelt administration, seeking to swap it out with a fascist dictatorship.


Aliens landed in Roswell

The 1947 "Roswell incident" spurred lots of conspiracy theories about flying saucers and extraterrestrials, as well as alleged U.S. government involvement in a cover-up about what really happened in the New Mexico town. What was it? Officially, the incident was attributed to a U.S. Army Air Force high-altitude ballon.


Missing POWs were left behind in Vietam

This conspiracy alleges that the United States left behind imprisoned prisoners of war after the war in Vietnam ended. The notion sparked outrage from families of missing POWs, who flew special black flags in protest so the U.S. government would be compelled to track down the missing soldiers. Despite the lingering doubts, the government's official response in 1993 was that there was no evidence to back up the conspiracy theory.

India is still a British colony

India officially ceased to be a British colony in 1947, but conspiracy swirled when Queen Elizabeth II allegedly visited the country without a visa in 1997, something that should only be possible within countries of the British Commonwealth. But the queen doesn't need a visa to travel anywhere in the world, and this conspiracy may have evolved from angry reaction to what was already a controversial visit by the queen.

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