His name: W. Mark Felt.
In May 1962, Felt was the special agent in charge of the FBI's outpost in Kansas City-know through the bureau as "the Siberia of Field Offices." When the call came in to the FBI's KC office that May 22 evening concerning a plane crash in northern Missouri, thunderstorms in the area was the likely cause.
But what began as a routine investigation, quickly moved to a serious criminal probe when Felt's team determined that a dynamite bomb had blown the Boeing 707 out of the sky.
In September 1962, Mr. Felt was removed from his exile in Kansas "Siberia" City and rewarded for his work on the flight 11 bombing when FBI Director J. Edgar Hoover moved Felt to Washington, DC.
In 1971 Hoover appointed Felt to the third-highest post in the FBI.
From his post at the FBI, Agent Felt secretly provided information to Washington Post reporters Bob Woodward and Carl Bernstein. That covert relationship between Felt and the Post reporters, led to revelations that President Richard Nixon was personally involved in the Watergate burglary scandal. Pres. Nixon eventually resigned from office, the only president in American history to do so.
After 31 years with the FBI, Felt resigned in 1973. His role as the Deep Throat source during Watergate wasn't revealed until 2005, when he outed himself.
Felt's 2006 memoir, "A G-Man's Life: The FBI, `Deep Throat' and the Struggle for Honor in Washington," on why he did it: "People will debate for a long time whether I did the right thing by helping Woodward. The bottom line is that we did get the whole truth out, and isn't that what the FBI is supposed to do?"
Mr. Felt died on Dec. 18, 2008 having done just that-not once in his FBI career?but twice.