Muhammad Ali, then known as Cassius Clay, won the heavyweight boxing championship for the first time on Feb. 25, 1964, defeating Sonny Liston on a technical knockout. He defeated Liston again in a rematch in Lewiston, Maine, in 1965. Here's AP's report from the Miami fight:
MIAMI BEACH, Fla. (AP) Cassius Clay, a 7-1 longshot, scored one of the major upsets in boxing history Tuesday night when Sonny Liston gave up the world heavyweight title in his corner because of a strained left shoulder.
As Liston failed to come out for the seventh round it went into the record books as a controversial seventh round technical knockout.
There was a chorus of boos from the small crowd of 8,000 in the Miami Beach Convention Hall at the ending. Liston had been cut under the left eye in the third round and looked slow and lumbering against the 22-year-old former Olympic champion from Louisville.
Clay, the fourth fighter with a perfect record to win the world heavyweight crown, leaped into the air at the sudden ending and opened his mouth wide as he yelled to newsmen, ''Eat your words!''
''I am the greatest, I am the greatest, I am the greatest,'' the new champion chanted ceaselessly after it was over.
''I'm the king of the world. I upset the world. I am the king. I am the king.''
Asked why Liston couldn't get to him, Clay said, ''Because I'm too fast. He was scared.''
''I am the greatest that ever lived. I just beat Sonny Liston and I just turned 22, so I must be the greatest. I was going to end it in the eighth as you would have seen, but the man stopped it in seven.''
The press almost unanimously had picked Liston to beat back the brash Louisville Lip, who had put on a frantic scene at the morning weigh-in.
Dr. Alexander Robbins, chief physician of the Miami Beach Boxing Commission, said, ''Liston strained his left shoulder. He couldn't lift his arm.'' ...
Bill Faversham, one of the 11 Louisville businessmen who have directed Clay's fortunes, said, ''We told them they gave us our chance and we'll give him his chance if we beat him. That was the word of a gentleman and we'll stand on it.''
Clay bounced around the ring waving to his fans and yelling, ''It wasn't any fix. I closed both his eyes. He didn't lay a hand on me.''
When the fight ended, Referee Barney Felix had scored the fight even. Judge Bunny Lovett had Liston on top, and Judge Gus Jacobson had Clay on top. The AP card had Clay ahead 4-2 in rounds.
Long before there was any talk of an injured shoulder, it was obvious that Liston was far from the ominous destroyer who knocked out Floyd Patterson in the first round of two title matches. This was his second defense.
When the ring announcer told the people that Liston had ''thrown his shoulder out'' in the sixth round, the crowd booed. The more cynical observers thought immediately of the possibility of a lucrative rematch.
Although the live gate was small, the closed circuit television for this fight reportedly set a new record of over 560,000 people. It was estimated that the closed circuit television take might send the total gate close to the $1 million mark.