What year did Muhammad Ali box Joe Frazier for the first time?

The "Fight Of The Century" took place on March 8, 1971, at Madison Square Garden. It was the first meeting of two undefeated heavyweight champions, since Ali (31-0) had not lost his title in the ring (been stripped because of his refusal to be inducted in the Armed Forces) and Joe Frazier (26-0, 23 KOs). Frazier won by unanimous decision and retained the title.

The Judges' scorecards results can be seen below

Referee: Arthur Mercante

Judge: Artie Aidala 9-6

Judge: Bill Recht 11-4

Judge: Arthur Mercante 8-6