Tommie Smith and John Carlos, who got gold and bronze in the 200m sprint, bowed their heads and raised a black-gloved fist during the American national anthem.
They also wore no shoes – only black socks – and Smith, who won in a world record time of 19.8 seconds, donned a matching scarf in their protest against racial prejudice.
While the action is now generally positively viewed as a seminal moment in the U.S. civil rights struggle, people then were appalled that politics was dragged into sport.
This was highlighted by a British Pathé newsreel, which described the victory ceremony as being 'unfortunately overshadowed by politics'.
Many in the crowd also booed the two Americans, who were joined on the podium by Australian silver medallist Peter Norman.
Afterwards, Smith said: 'If I win I am an American, not a black American.
'But if I did something bad then they would say ‘a Negro’.
'We are black and we are proud of being black. Black America will understand what we did tonight.'
Smith said he had raised his right fist to represent black power in the U.S., while Carlos raised his left fist to represent black unity.
Together they formed an arch of unity and power.
He said the scarf represented black pride and the socks with no shoes stood for black poverty in racist America.
Carlos also claimed he had his tracksuit top unzipped to show solidarity with all blue collar workers in the U.S.
And he wore a necklace of beads, which he said represented 'those individuals that were lynched, or killed and that no-one said a prayer for, that were hung and tarred. It was for those thrown off the side of the boats in the middle passage'.
It later emerged that both U.S. athletes had intended to bring a pair of black gloves to the event, but Carlos forgot his.
It was Norman who suggested that Carlos wear Smith's left-handed glove.
The white Australian, who was opposed to racist policies in his own country, joined Smith and Carlos in wearing Olympic Projects for Human Rights (OPHR) badges.
Within days, the two Americans, who were both students at San Jose University, had been evicted from the Olympic Village and suspended form the U.S. team.
Longtime IOC chief – and fellow American - Avery Brundage had threatened to ban the entire U.S. track team if Carlos and Smith were not barred from competing.
One of the objectives of OPHR had been to oust the ageing Brundage, who had not objected to the Nazi salutes at the 1936 Berlin Games.
He had also fought to keep South Africa in the IOC and was accused of anti-semitism after refusing to stop the 1972 Games following the murder of 11 Israeli athletes.
On Smith and Carlos’s return to America, they received a mixed welcome – greeted as heroes by many some and sent death threats by others.
They have since been honoured for their part in advancing the civil rights movement in America.
Norman was reprimanded by his country's Olympic authorities not picked for the 1972 Games, despite having qualified 13 times over.
Smith, who is now 69, and Carlos, 68, were pallbearers and gave eulogies at Norman's funeral following his death from a heart attack at the age of 64 in 2006.