Warning: These 10 historical conspiracies will shatter your basic understanding of history—keep reading if you dare to question the “truths” you’ve always believed.  
TOP 10: The San Diego Plan

The San Diego Plan is an anonymous manifesto that basically calls for Texas, Colorado, Arizona, California, and New Mexico to secede from the U.S. and later merge with Mexico.  The most controversial part?  It advocates killing every white male over the age of 16 living in those states.  This conspiracy theory took off because: a) no one knows who wrote the manifesto, and b) people believe it originated in Mexico and was sent to neighboring states to stir up dissent—even rebellion.

TOP 9: The “Existence” of D.B. Cooper


D.B. Cooper is the alias of an unknown man who hijacked Flight 305 from Portland, Oregon, to Seattle, Washington, demanding $200,000 in ransom for the hostages.  Here’s the twist: conspiracy theorists claim D.B. Cooper never even existed.  They say he was a made-up story by the four flight attendants on board, who ultimately split the ransom money among themselves.

TOP 8: The Donation of Constantine


The Donation of Constantine is a decree supposedly signed by Emperor Constantine I, in which he handed over control of Rome to the Pope back in the 4th century.  But here’s the conspiracy (and the truth): this document was proven a forgery in the 1400s.  By then, though, the Pope and the Catholic Church had already gained massive influence over most of Europe—and beyond.

TOP 7: The Phantom Time Conspiracy


In 1991, German historian Heribert Illig proposed a shocking theory: Emperor Otto III and Pope Sylvester II made up nearly 300 years of history.  Why?  To make Otto III’s reign as Holy Roman Emperor fall after the year 1000 AD—a number considered highly significant at the time.  If this were true, even well-documented historical figures like Charlemagne (famous for uniting much of Western and Central Europe) would be total fabrications.  Historians later debunked this theory, but some fringe scholars still swear by it.

TOP 6: The Sinking of the USS Maine


In 1898, the USS Maine battleship sailed to Havana, Cuba, to protect U.S. interests.  But then an explosion on board sank the ship, killing almost everyone on board.  This event became the spark that ignited the Spanish-American War.  Conspiracy theorists argue the explosion wasn’t an accident or a Spanish plot—it was an inside job by the U.S. government, designed to give them an excuse to go to war with Spain.

TOP 5: Charles Manson and the CIA


Charles Manson is infamously known as the cult leader of the Manson Family, which gained notoriety for the murders of Sharon Tate and her friends.  Conspiracy theorists claim Manson was involved in the CIA’s MKUltra program—a shady human experimentation project.  The CIA allegedly developed and tested drugs for interrogation, and even used mental and psychological torture and brainwashing to force confessions.

TOP 4: The Sinking of the Titanic


Conspiracy theorists claim the Titanic’s 1912 sinking wasn’t an accident—and it wasn’t even the Titanic that sank.  Instead, they say it was its damaged sister ship, the RMS Olympic, in a plot by industrialist J.P. Morgan (with stakes in White Star Line).  Morgan’s motive?  Collecting a big insurance payout and eliminating millionaires on board who opposed his financial plans.

TOP 3: The Identity of William Shakespeare


William Shakespeare needs no introduction—Romeo and Juliet, Macbeth, Othello, and A Midsummer Night’s Dream are just a few of his famous plays.  But conspiracy theorists argue that the man known as William Shakespeare didn’t actually write any of the works attributed to him.  Theories vary: some say Shakespeare was a pseudonym for a nobleman who didn’t want his identity revealed, while others claim “Shakespeare” was a composite of multiple people, not a single individual.

TOP 2: Jack Ryan as CIA Propaganda


Tom Clancy’s Jack Ryan series follows a former Marine turned CIA agent on high-stakes missions.  Conspiracy theorists call it pro-CIA propaganda, citing President Reagan’s public praise (he even labeled the books “required reading” for his security team).  They argue the CIA collaborated with Clancy to craft a heroic Jack Ryan, boosting the agency’s image amid post-Vietnam skepticism.

TOP 1: The Faked Moon Landing


Despite being fully debunked, some skeptics insist the 1969 Apollo 11 moon landing was faked to win the Cold War Space Race.  They point to “flaws” in footage—no stars, a waving American flag (no lunar atmosphere), and uneven lighting—as proof it was a Hollywood-style production filmed in a secret studio, even dismissing Neil Armstrong’s iconic “giant leap” line as part of the ruse.