Americans love a good conspiracy theory. It brings out the amateur detective in all of us as we speculate about the meaning behind this piece of evidence versus that, about the motives behind a particular event and about the loyalties and psyches of the key players involved.

Perhaps no single event in American history has captured the imagination of conspiracy theory buffs more than the assassination of President John F. Kennedy. In the 50 years since that historic event there have been countless books, movies and documentaries, and more than one official investigation, into exactly who is responsible for JFK's murder and why.

To recap, Kennedy was assassinated at 12:30 p.m. Central Time on Friday, Nov. 22, 1963 as his motorcade drove by the infamous grassy knoll through Dealey Plaza in Dallas. Within hours police arrested Lee Harvey Oswald, a former U.S. Marine who defected to the Soviet Union in October 1959 and returned to the U.S. in June 1962. Two days later, before he could stand trial and answer some key questions about Kennedy's assassination, Oswald was gunned down by Dallas nightclub owner Jack Ruby.

A 10-month investigation in 1963-64 by the Warren Commission concluded that Kennedy was assassinated by Oswald, acting alone, and that Ruby also acted alone when he killed Oswald. But that did nothing to quell the growing speculation that Oswald did not act alone, that indeed he may have been a patsy for the CIA, the Soviet Union or organized crime. There's further speculation that Ruby killed Oswald, under orders from some unknown group, as part of a cover-up.

Polls conducted between 1966 and 2003 found that as many as 80 percent of Americans suspect there was a plot or cover-up involved with Kennedy's assassination. And in 1979 a U.S. House Select Committee on Assassinations concluded that JFK was probably assassinated as a result of a conspiracy.

The HSCA stated there were at least four shots fired at the president's motorcade that day, only three of which could be linked to Oswald, and that there was "a high probability" that two gunmen fired at the president. The committee ruled out direct involvement by the CIA, the Soviet Union or organized crime, but not individual members of those groups.

The acoustical evidence of that committee's report has since been discredited, but that has done nothing to stop the speculation that something more sinister than a lone gunman was amiss that day 50 years ago.

What is it about the Kennedy assassination that has generated so much intrigue over the years? Certainly the limited amount of definitive forensic evidence and the contradictory eyewitness accounts have contributed to the abundance of conspiracy theories, as did the fact that Oswald was murdered before he could stand trial. More than that, however, was the loss of a beloved president and the endless wonder of what might have been had he lived.

Kennedy's assassination represents the end of an era: The Age of Camelot came to a grinding halt and American innocence was lost that day. What followed in the wake of his murder was a decade of war in Southeast Asia, internal strife right here in America, a cultural revolution that pitted the youth movement against the older generation, the Pentagon Papers and the Watergate scandal that forever tainted our trust in our own government.

Conspiracy author Jim Marrs writes in his book "Crossfire" about what kind of America we might have today if President Kennedy had lived: "Imagine the United States if there had been no divisive Vietnam War, with its attendant demonstrations, riots, deaths, and loss of faith in government. There may not have been the scandals of Watergate, other political assassinations, or the Iran-Contra Pentagon-CIA attempt at a 'secret government.' Detente with Communist Russia and China might have come years earlier, saving hundreds of millions of wasted defense dollars -- dollars that could have been put to use caring for the needy and cleaning up the environment. Picture a nation where no organized-crime syndicate gained control over such divergent areas of national life as drugs, gambling, labor unions, politicians, and even toxic waste disposal."

That indeed sounds like utopia, and many believe Kennedy was headed in that direction, and that a great symbol of progressive liberalism was snuffed out that November day in 1963.

However, as with all the rebuttals to the conspiracy theories surrounding Kennedy's assassination, there are those who dispute this view of an alternate America had our 35th president lived.

"The fact of the matter is that the real JFK bears no relation to the progressive martyr envisioned by Oliver Stone, Jim Marrs, and by numerous members of Internet newsgroups," notes Eric Paddon, a history professor at Wheaton College. "In order to promote the idea of JFK as 'progressive,' they have asserted some strange things that even liberal historians would find very puzzling."

For one thing, he said, far from being a progressive liberal, JFK was a moderate-centrist with viewpoints that were considerably to the right of the Democratic party's liberal wing. He was stand-offish toward the Civil Rights movement and cut the capital gains tax. He was a Cold Warrior and anti-communist, and was friends with and politically supported Eugene McCarthy.

The unfortunate truth is that we will never really know for sure what kind of world we would have today if Kennedy was not assassinated. Everything about that alternate timeline is pure speculation. So it also goes with the verdict who really killed Kennedy and why. There are simply too many unanswered questions and too much room for speculation to ever have any definitive answers.

And therein lies the root of all conspiracy theories and explains how they are able to persist through the years. No doubt people will still be offering all kinds of conjecture about Kennedy's assassination 50 years from now.