The 48th anniversary of President John Fitzgerald Kennedy's assassination occurs this month. It is quite amazing that all these years later the circumstances of his death are still under discussion.On Nov. 22, 1963, Kennedy was killed by a gunshot wound to the head at Dealey Plaza in Dallas, Texas, where he was traveling in a Presidential motorcade. Lee Harvey Oswald was proven to be the assassin; he was killed by Jack Ruby two days after shooting JFK. During the investigation into President Kennedy's death, Supreme Court Chief Justice Earl Warren, who led the investigating commission, came to the conclusion that Harvey acted alone. Despite this verdict, many Americans believe there is more to this story than meets the eye. In a poll conducted in 2003 for the 40th anniversary of the event, 75 percent believed that JFK's death was part of a broader plot. Conspiracy theories abound as to who was involved. Here are some of the more interesting ones.Some people think JFK was killed by angry Cuban exiles who believed he sold them out during the Bay of Pigs invasion in April 1963. In that conflict, President Kennedy refused to allow the United States' forces to participate, leaving the Cuban exiles involved at the mercy of Fidel Castro's forces. Consequently, thousands of émigrés were imprisoned or killed by Castro and his regime. Fidel Castro himself figures into another conspiracy theory. Believers of this theory claim that Castro had JFK killed in revenge for the United States government's numerous attempts on his life.A third of the numerous conspiracy theories surrounding JFK's assassination is that the KGB was responsible, killing Kennedy in retaliation for his embarrassment of them in the 1962 Cuban missile crisis. In this theory, Oswald, who once defected to the Soviet Union and had a Russian wife, was persuaded by them to kill the president. Another theory blames wealthy Texans. This theory claims that JFK was assassinated by powerful Southwesterners who were angry at Kennedy for a tax reform plan that would reduce or eliminate the tax credit that oil companies received. Although there are countless conspiracies surrounding Kennedy's death, what's more important than how he died is that he did. America lost an outstanding president on the afternoon of Nov. 22, 1963. No matter the circumstances, JFK's assassination changed the heartbeat of the United States.