Scandal at the end of the 200m
When the three athletes who had just dominated the 200m final climbed onto the podium to receive their medals, the crowd in the Aztec stadium had their eyes pinned on the winner Tommie Smith.
In covering the distance in 19.83 sec the American had set a new world record, beating Peter Norman of Australia and fellow American John Carlos.
If the race remains a cherished sporting memory, then the medal ceremony would become etched into Olympic history.
When the athletes arrived at the foot of the podium spectators saw that the two Americans were wearing a black glove on one hand, their shoes in the other and sporting a badge with the words "Civil rights", a badge also worn by Norman in solidarity.
And as the American national anthem played and the stars and stripes flag was raised to the sky, the two black athletes, in their socks, lowered their heads and lifted a clenched fist in a black power salute. Their protest was against racial inequality back home in the United States, their barefeet, they explained, a reminder of black poverty.
They wanted to tell the world that the ideals of liberty expressed in the Star Spangled Banner were only relevant to the white community.
John Carlos explained to journalists: "White America will only give us credit for an Olympic victory. They'll say I'm an American, but if I did something bad, they'd say I was a Negro".
Officials were incensed by this protest. The International Olympic Committee wanted them punished. The Americans reacted by suspending the two men, ordering them to leave the Olympic village and Mexico within 48 hours.
As a gesture of support at the end of the 400 metres, the next day three black Americans - Lee Evans, G. Lawrence James and Ronald Freeman saluted the crowd with raised fists, black berets and smiles.
Evans, who took gold, had to be persuaded to compete by Carlos and Smith.
International opinion regarded Smith and Carlos in a sympathetic light, but they got a frosty reception on their return home. Shunned and without any proper work, they also suffered broken marriages.
Eventually, in 1972, Smith found work as a trainer at Oberlin College, Ohio. Six years later, in Santa Monica, California, he started a support programme for children from the ghettoes.
As for Carlos, he was asked by the Games' organisation committee to promote the 1984 Los Angeles Games in the ghettoes.
Copyright 2012 Agence France-Presse.