(crowd cheering) - This is the stadium at Rushcutters Bay in Sydney, Australia, on December 26th, 1908.

20,000 spectators watch as Jack Johnson prepares to throw his final punches and knock out Tommy Burns to become the first Black Heavyweight Champion of the World.

(whooshing fists) The overwhelmingly white crowd holds its breath and reporters prepare to file their stories.

(upbeat music) Sports has always been a revealing mirror of our culture.

It's where many white Americans are made to confront what is happening with race in America.

Sports is where boundaries get challenged and broken as we watch it all happen out in the public arena.

That's one of the reasons I made BASEBALL.

I wanted to tell the story of Jackie Robinson, because it shows America coming to terms with its complicated past.

(crowd cheering) It's why right now I'm working on a film on Muhammad Ali, whose greatness, both as a boxer and a human being, exploded many white people's notions of what Black athletes and more importantly, Black Americans could be.

But while Robinson and Ali are examples of athletes breaking barriers and pulling the culture forward, I want to show you this story from decades earlier, of what happened when an African American boxer was about to knock out a white man to become the Heavyweight Champion of the World.

And what happened at this moment?

Just as Johnson was about to deliver his final blows?

Watch.

(bell rings) - [Narrator] Finally in the 14th round, as Johnson moved in for the kill, the police stopped the fight to save Burns further humiliation and ordered the movie cameras to stop grinding.

- When finally Burns is about to be knocked out, the world is spared the spectacle of a Black man knocking out a white man.

And the world is denied access to this historical moment because the white supremacy of the universe in 1908 is so demented and extreme the knockout is stopped and the film is stopped.

- The police stop the fight.

Not only do they stop the fight to spare everyone seeing a Black man knock out a white man, they order the cameras turned off as well.

And two years later, in 1910, Johnson beat Jim Jeffries, and what happened?

Nationwide white on Black race riots erupted.

(crowd cheering) In my films, I always look to explore subjects that reveal something telling and crucial about the American story.

And for me, sports can serve as a kind of x-ray of the health of America.

It's where we get a unique and raw sense of where we are as a country.

(upbeat music)