Over the years, those theories sprawled, and the government made some of its document hoard public.
Seeking to settle the matter once and for all, Congress passed a law
25 years ago mandating the government release all its documents and giving agencies a long window to keep sensitive information secret.
In keeping with that law, President Donald Trump issued a memo
Thursday evening blocking some of the files from seeing the light of day, at least temporarily. However, Trump's memo did not block 2,800 government documents relating to the assassination -- from a total that once made up millions -- from release.
Trump tweeted his excitement on Wednesday -- as he headed to Dallas for a fundraiser -- saying it is "so interesting!"
The National Archives sought to temper expectations, warning the most explosive documents have likely already been released, but the deadline of the JFK Records Act, set 25 years ago, could breathe oxygen into some of the many competing theories.
After Kennedy's death, President Lyndon Johnson ordered an independent inquiry into it and named Supreme Court Chief Justice Earl Warren to lead that team, known as the Warren Commission. The commission's historic report
declared Lee Harvey Oswald acted alone and without assistance to kill Kennedy before Jack Ruby murdered Oswald while in custody.
Oswald was a former Marine who moved to the Soviet Union for a few years before coming back to the US. His association with communist elements and brief trip to Mexico City shortly before he appeared in Dallas are of interest for those who plan to sift through the unreleased files.
The Warren Commission report continues to face heavy skepticism from people advocating alternative theories, and a poll
taken around the 50th anniversary of the Kennedy assassination showed the majority believed more than one person was involved, showing popular suspicion for the idea Oswald acted alone.
Here are a handful of the most popular and well-known conspiracy theories about the assassination:
The House of Representatives Select Committee on Assassinations report also concluded
Oswald fired on Kennedy, killing the President, but differing with the Warren Commission, the House report said
there was a "high probability" that two gunmen fired at Kennedy, offering skeptics of the Warren Commission endless fodder.
The term "grassy knoll" now recalls the theory that Kennedy's killer was not necessarily Oswald, but instead a man firing from the ground along the route of Kennedy's presidential motorcade.
Trump world finger-pointing
Trump's longtime associate Roger Stone is a passionate conspiracy theorist, who now works for the fringe, far-right website InfoWars.
Stone is an advocate for the full release of the files and authored a book pointing the blame for the assassination at Kennedy's vice president and successor, Lyndon Johnson.
North Carolina Republican Rep. Walter Jones, a leading congressional advocate for the full release of the files, told CNN he spoke with Stone about pressing Trump not to block the disclosure.
And like his friend Stone, Trump himself has tossed out his thoughts on the assassination, pointing during the campaign to Sen. Ted Cruz's father -- without evidence -- as someone potentially involved.
One of the most popular theories, and one featured in popular culture from Oliver Stone's film "JFK" to Don DeLillo's novel "Libra," is the idea the CIA or people associated with the CIA were involved in some way in the Kennedy assassination.
Some theories go far enough to suggest a CIA-affiliated person fired the deadly shot, while others state the CIA or other government agencies had knowledge there would be an attempt on Kennedy's life and, by not acting, they were complicit in the murder.
Rep. Jones suggested he belongs to the camp that believes there was likely some agency involvement or inaction and said he believes the release could help settle the matter.
"The government owes the American people the truth," Jones said. "And if you were complicit then so be it. 'Fess up to it."
The House report said
the CIA "was deficient in its collection and sharing of information both prior to and subsequent to the assassination."
When Fidel Castro led a communist revolution in Cuba, the US recoiled as the ideological brethren of its Cold War enemies found a foothold not far off from its own shores. Kennedy greenlit an operation, known as the Bay of Pigs, early on in his presidency, in a failed attempt to topple the Castro government.
Incidentally, the botched operation, among other things, led Kennedy to criticize the CIA, and a New York Times report
quoted Kennedy as saying he wanted "to splinter the CIA in a thousand pieces and scatter it to the winds."
After the Bay of Pigs and the Cuban Missile Crisis, the US continued plotting
to kill Castro for years, including trying to poison the autocrat's cigars.
Given the potential motive and Oswald's communist leanings, one theory posits Castro had a hand in the killing.
For his part, the now-deceased Castro reportedly said
after the killing: "This is bad news."
One theory pulls away some of the Cold War mystique and the potentially crazed lone wolf idea. Instead, it posits the Kennedy assassination was a mafia hit, although possibly one with CIA complicity.
Kennedy appointed his brother Robert as attorney general, and the younger Kennedy made going after organized crime one of his top priorities. Moreover, Castro's revolution pushed out elements in Cuba that were friendly to mafia interests.
The House investigation said
its evidence showed the mafia was not involved in the assassination, but would not rule out the involvement of members of the mafia.
Kennedy was not the target
Kennedy was not alone in Dallas. First lady Jackie Kennedy was by his side, as was Democratic Texas Gov. John Connally.
The governor also took fire when Kennedy was killed, and one theory says Oswald meant to kill the governor, not Kennedy.
The journalist James Reston Jr. outlined
this theory at length, saying Oswald drew a dagger dripping with blood through Connally's name, and noted Oswald's wife said Connally was his target.