The Most Widely Believed Conspiracy Theories in US History

Some people (occasionally known as "Truthers") believe that the 9/11 terrorist affront that killed 3,000 Americans on September 11, 2001, were actually orchestrated by the United States government or a group other than al Qaeda. Believers of the conspiracy argue the World Trade Center's Twin Towers fell and continued to burn in the aftermath in a way that suggests it was a controlled demolition. Others argue the United States government was aware of 9/11 prior to the event and allowed them to happen by declining to intervene. This theory was mentioned in the Michael Moore documentary Fahrenheit 9/11, especially the idea that then-President George W. Bush was supposedly briefed on the plans for offense and chose to ignore them.

On November 22, 1963, President John F. Kennedy was shot as he was riding in a presidential motorcade in Dallas, Texas. According to an investigation known as the Warren Commission, Kennedy was shot by sniper Lee Harvey Oswald, who acted alone (and was murdered by nightclub owner Jack Ruby days later). However, some believe that the Warren Commission was simply a means to cover up a conspiracy to kill Kennedy. Many allege that conflicting facts regarding the murder weapon, witness accounts and the autopsy of Kennedy suggest a coverup. Though few speculate as to the identity of the actual alleged killer, the CIA, KGB, Mafia, Federal Reserve, Fidel Castro, and sitting Vice President Lyndon B. Johnson were all mentioned as possibilities by various conspiracy theorists.

Though many believe that NASA's Apollo 11 landed on the surface of the moon on July 20, 1969, many also believe that the famous "one small step for man, one giant leap for mankind" moment was faked. The moon landing hoax is one of the most well-known conspiracy theories with arguments continuing decades later about the event. Proponents of the hoax theory claim the United States faked the moon landing to win the space race and ultimately the Cold War with the Soviet Union. To do this, accusers claim the evidence of the astronauts on the moon was filmed in a sound stage in Hollywood based on a script created by Arthur C. Clarke and directed by Stanley Kubrick.

Mentioned in the alien invasion movie Independence Day among others, Area 51 is a United States Military base that operates as part of Edwards Air Force Base in Nevada. Due to the intense security surrounding the remote installation, including that the US Government would not acknowledge the existence until 2003, many have speculated Area 51 is actually used to hide alien spacecraft that have crashed into the Earth. In July 1947, many claimed that an unusual object believed to be a UFO crashed in nearby Roswell, New Mexico. Conspiracists claim the Roswell incident is only one of several alien crash sites in the country with Area 51 used for alien autopsies. UPDATE: The existence of the covert Area 51 has been officially confirmed by the CIA in newly declassified documents obtained by George Washington University. The report documents the development of the secret U-2 spy plane, the history of how the covert area came into existence, and points to the precise location on an Atomic Energy Commission map. Because of the developmental plane's never-before-witnessed operating altitude and the way the silver wings would reflect the sun — seeming to be on fire — the UFO sightings started pouring in to air traffic controllers and the Air Force. The Air Force recorded the reports in their Operation BLUE BOOK, and investigators tried to calm concerned citizens by attributing the sightings to natural phenomena because they could not reveal the true, but classified, cause.

Alleged by so-called "birthers," some people believe Barack Obama, the 44th president of the United States, was not actually born in Hawaii as he claims, but that he was born in Kenya and not eligible to serve as president. Despite Obama releasing copies of his birth certificate in 2008 and 2011, the birthers persist that Obama is not a natural-born American. Numerous politicians have questioned Obama's citizenship including many from the Republican and Tea Parties like Sarah Palin, Michele Bachmann and Donald Trump. Others have suggested Obama is a Muslim rather than the Christian he claims. Opponents of the birthers claim this is nothing more than misdirected racist remarks at the first African-American president.

After 9/11 mastermind and al Qaeda leader Osama bin Laden was killed by US Navy Seal members on May 2, 2011, some argued the way his body was buried, lack of evidence of the death and the failure to keep the public in the loop suggested a conspiracy. Shortly after his death was announced by President Barack Obama, conspiracists stated that because bin Laden's body was nearly immediately buried at sea and because Obama declined to release photos of a dead bin Laden or the video of the raid, that bin Laden was in fact alive and well. Despite al Qaeda acknowledging the death of bin Laden, some argued the story was fabricated by Obama to secure re-election or take the heat off his birth certificate controversy. Bill Warren, a diver from California, took the conpspiracy theory so far that he announced a plan to search the waters for bin Laden's body.

Also called climate change, global warming refers to the rising temperature of Earth's atmosphere and oceans as a result of greenhouse gases. To reduce the effects of global warming, activists and lawmakers have proposed a number of changes, including regulating burning fossil fuels and stopping deforestation. Some believe that global warming is a hoax, however, and that the data used to suggest a climate change is bogus. Others suggest these climate changes are not a result of humankind, or that steps other than those suggested need to be taken to prevent further damage.

Just as some claim the US Government was aware of 9/11 before it happened, some allege the Japanese operation on December 7, 1941, was known of by the government before it happened. Many have alleged that despite having advance knowledge of the potential fatalities, the operation on the Hawaiian naval base was allowed to happen as a means to get the United States into war. Ten separate inquiries into the affront were made between 1941 and 1995 to determine if any high-ranking officials, including former Secretary of the Navy Frank Knox and former President Franklin D. Roosevelt, were aware of the operation before it occurred.