The 1965 rematch may well be the most controversial fight in history.
Ali raced out of his corner, landed punches to Liston's head, and Liston collapsed to the canvas.
Yet scrutiny of the fight film still makes it difficult to see the actual punch which did the damage. It has become known as the "phantom punch", with claims that Liston took a dive.
The confusion didn't stop there. As the famous photo portrays, Ali taunted the fallen Liston, calling on him to get up.
"Get up and fight, sucker," is the famous quote.
What the photo doesn't portray is that Liston did get up.
The referee Jersey Joe Walcott - himself a former champ - wanted Ali to go to a neutral corner, because only then can the count begin, the eight-second mark qualifying as a knockout.
As the records show, the punch was landed 1m:42s into the fight, and the knockdown timekeeper got to 22 seconds before Liston reached his feet again, and attempted to continue. Urged by a ringside voice, Walcott called the knockout victory to Ali, even though Ali had not gone to the neutral area.
The memorable moment, of Ali snarling while apparently swiping a right hand, was caught by photographers Neil Leifer and John Rooney.
Rooney's black and white photo taken with a 35mm SLR camera produced a rectangular frame. He worked for Associated Press, and his photo was used around the world. It was seen as almost the perfect sports photo, even though the moment it apparently captured - of victory - did not accurately depict what was happening.
But a colour photo by Sports Illustrated's Leifer is regarded by some as even better, the real perfect shot.
Leifer became one of sport's finest photographers. His shot of Ali over Liston is taken with a Rolleiflex, giving a square frame. The two boxers fill the frame in a more imposing way, with the blackened arena above Ali heightening the drama.
They are both amazing photos.
Leifer produced his own count for that night.
"I will never have a night like that ever," he said.
"The fight went two minutes and eight seconds…I got three great pictures."
Ali's life needs no introduction. He will always be the most extraordinary sportsperson of all time, whose life reached well beyond the ring.
Liston led a troubled life, but was a far better boxer than the image portrayed by the iconic photos, suggestions he took a dive and the famous stories about how he was talked into defeat by a young Ali.
ESPN even rated him the second hardest puncher in history, behind Mike Tyson, and he makes most top 10 lists on that score.
Five years after the phantom punch controversy, Liston was dead, heroin found near his body. Some associates attest that he never used the drug, along with claims that he was murdered by the mob.
