Speaking exclusively to SSN's Mike Wedderburn about his famous gesture, Smith explained what the protest was about, the personal cost, its impact, the importance of young people speaking out, and explained why he is hopeful for the future.
The protest by Smith and John Carlos 53 years ago was seen on colour television and captured by photographers as it became one of the most iconic sporting images of the 20th century.
The two athletes took off their shoes and wore black socks on the podium to highlight black poverty. Smith also had a black scarf to represent black pride, while Carlos had a necklace of beads to remember people who had been lynched.
They raised their fists in black gloves as the national anthem of the United States played to show their support and solidarity with Black people and racial injustice in the world.
How did it feel to protest at the top of the podium?
"It felt a sense of pride, a holy divine, that I was put there to serve a purpose," said Smith, who is now 77.
"That divine movement to ask people to please understand that this is a move in justice, a move in freedom."
"A moving insight of the need to perform the understanding of love and respect. Tommie Smith wasn't standing on that victory stand for hate. I have never been a hateful person. My whole background has been from the Christian experience.
"But I had at that particular time the responsibility of standing because I was asked to stand for what I believe in. And I still do that today.
"No hate. It was not a hateful thing. It was not a degradation confronting the flag. We represent that flag with pride because a lot of our people died so this country could make a formation of justice."
All three medallists on the stand: Smith, Carlos and Australian Peter Norman chose to wear Olympic Project for Human Rights (OPHR) badges.
Smith says: "The Olympic Project, not for Black rights, it was for human rights. For people, for human rights. I do believe that's why it spanned the entire globe."
Smith and Carlos were studying at San Jose State University before the Olympics and were part of the famous 'Speed City' generation of great runners.
They were inspired by civil rights activist and academic Dr Harry Edwards who co-founded the OPHR. The organisation fought against racial injustice and racial segregation.
On the track, Smith won the national collegiate 220-yard title in 1967, and also won the Amateur Athletic Union 200m in 1968 to make the US Olympic team.
In the 200m Olympic final he came from behind to overtake Carlos and win a gold medal in a world record time of 19.83 seconds. He even had time to celebrate by raising his arms in triumph before crossing the finishing line.
It was the first time any athlete had finished legally in under 20 seconds over that distance. Smith's record stood for nearly 11 years. Peter Norman pipped Carlos to get silver. With Carlos getting bronze the American pair would both be on the podium.
Although there was talk of an Olympics boycott, it did not materialise. Smith says the athletes decided it would be better to compete in Mexico City for "the sake of social understanding." He added it was left up to each athlete to decide how they would protest if they wanted to.
In an interview earlier this year Carlos told Sky Sports News how their protest "was conceived roughly 30 minutes before we went out on the podium."
Talking about the protest, Smith said: "Would you believe I was heard without a word uttered? The need for justification, the need to be united as one - to love and respect."
"John Carlos and Tommie Smith stood for the righteousness of justice. And the freedom of speech and the declaration that this would be a non-violent protest.
"This was our way of standing to emphasise the need and the love and respect, the understanding, the conversation of athletes who had something to say. I believe at that particular time all athletes had something to say.
"But there were those who preferred not to say anything and live under the injustices that had already been thriving in a system of racism and degradation.
"It was my pride and justice to represent a country that I love because of what I went through to get to where I was, what I was given to get to where I was, so I could stand up, smile and look at the folks and say, 'this is how Tommie Smith sees it and this is how it will be'."
Wyomia Tyus, who a day earlier became the first athlete to win the 100m at consecutive Olympics, was inside the stadium to see the reaction to the protest.
She said: "You had people talking, you hear yelling and screaming, whistling, booing, and all these kinds of things that were going on. Immediately, I went, 'oh my gosh, they could get killed'. Something could really happen to them.
Within minutes Tyus left the stadium with another US athlete because they were worried for their own safety.
For their gesture, Smith and Carlos were suspended from the Olympic team and had to fly home. Both men received dozens of death threats on their return. They also struggled to find work and new jobs.
There was also negative criticism in the media and both faced discrimination and harassment. In an interview last year Smith revealed he still receives death threats and hate mail.
Tom Ratcliffe, the director of the 2020 documentary The Stand: How One Gesture Shook The World, said: "The large majority of the United States thought what they did was treasonous."
The death threats were also aimed at Smith's family and, although he expected "trials and tribulations", he says he did not understand the scale.
Smith says: "I had really very little idea of what type of hurt or harm, and danger that that would put me and my family in."
The sprinter is the seventh of twelve children and says some of his younger siblings were "scorned to a certain point" because many viewed his gesture as a negative and hateful act. Some were too young to understand the context of what had happened.
His brothers lost their place on their high school football team and the only job he could get was washing cars.
He faced poverty despite being an Olympic gold medallist and world record holder. His mother also received hate mail and died of a heart attack in 1970.
As well as being an Olympic champion Smith set 13 world records during his running career, and held 11 simultaneously.
Although he would never go to another Olympics, Smith switched sports and played three seasons of professional football for the NFL team Cincinnati Bengals where he spent most of the time on the practice squad.
Smith, who had already got a degree from San Jose State in 1969, got a master's degree in social change in 1976. He taught and coached at Oberlin College in Ohio for six years.
The 200m Olympic champion then taught sociology, was a Professor in physical education and worked as a coach at Santa Monica College in California for 27 years.
In 2005 his old university San Jose State built a 22-foot statue of the American athletes on campus recreating their iconic protest. They also awarded them honorary doctorates.
In recent years Smith has continued to use his voice in interviews and documentaries and works with young people across the country as part of the Tommie Smith Youth Initiative which uses athletics and health to mentor young children to lead better lives.
"I don't want to embarrass you, but I want to ask you, would you say you are an inspiration?" asks Sky's Mike Wedderburn.
"I'm not perfect. I'll leave that with you," Smith says from his home in Atlanta.
For many in the US and around the world, Smith and Carlos are an inspiration. Among the generation who grew up with the image. In schools. Among the African-American population. And athletes too.
Lewis Hamilton raised his fist on the podium at last year's Styrian Grand Prix to emulate the gesture by Smith and Carlos. He said last year he had been "inspired" by the image and reading about the protest.
Smith received the Courage of Conscience Award from the Peace Abbey for his lifelong commitment to athletics, education and human rights.
40 years after their protest, Carlos and Smith were awarded the Arthur Ashe Courage Award at the 2008 ESPY Awards. Awarded by ESPN, ESPY Award is short for Excellence in Sports Performance Yearly Award.
In 2018, the USA Track & Field celebrated the achievements of the athletes at the 1968 Olympics. At the USATF Night of Legends Gala, Carlos and Smith presented the Jesse Owens Award for male athlete of the year.
They got a standing ovation after being introduced by Colin Kaepernick who said on a video that the pair "had an impact on the heart and mind of millions and have been a huge inspiration to me, personally."
Carlos and Smith were also inducted as Legends into the United States Olympic and Paralympic Committee (USOPC) Hall of Fame in 2019.
51 years earlier the same organisation had suspended them and kicked them out of the Olympic village under pressure from the International Olympic Committee.
What does Smith think about progress when he sees US athletes and football players in the UK take a knee before games?
"I think we've learnt that it is a long way to go in the effort of understanding, of love and of respect," he says.
"I'm sure those soccer players and those basketball players, the women and the men can understand that yes, there is a difference. The most difficult thing in understanding is the knowledge of your inside, how you feel about a colour.
"If we can get past that colour and start coming from the heart out, seeing a human instead of a colour of the human, I think that's a big step.
"It is a coming together of athletes because we are beginning to talk now, the younger generations are beginning to talk. And there's no such thing as perfection. There's working toward the freedom of feeling a need to understand and to love.
"To talk without knowing, without understanding that, 'Oh, I'm better than you because I'm a white person or I am less than you, because I didn't have what you have to get to where I am'. So it's the understanding of the biasedness that's killing instead of togetherness that is a new birth."
In 2016 Colin Kaepernick decided to take a knee to protest against police brutality and racial inequality in the United States. Many compared it to the stand taken by Smith and Carlos.
What did Smith think when he saw it? "It's working. Just that. It's working."
Smith adds: "The move to do something by Colin had come into his body, into his mind, into his thought process of making a change.
"He made that change by sacrificing his life, by sacrificing his future. Otherwise, it would not have been done. There have been people dying in the streets longer before Colin.
"But there was nobody to take that place of Colin Kaepernick. He had to do that himself. He was born to do what he did otherwise it would not have been done.
"To stand by Tommie Smith, John Carlos or Colin Kaepernick and hundreds and hundreds of thousands of other young athletes, understand that I have a reason for being here, and I'm going to do what I think is necessary to bridge that gap of misunderstanding. Or bridge the gap of 'I'm not saying anything because I'm embarrassed, or I might have too much to give up'.
"Sometimes we have to be charged because that charge you must keep. And move forward with that feeling of sacrificial movement. Not movement for money every day. You must give up to receive."
Five years ago, Carlos and Smith were special guests at the White House as President Barack Obama welcomed the 2016 US Olympic and Paralympic teams after the Rio Games.
Sitting a few rows from the front, they watched as Obama highlighted their stand in 1968 and said it was "controversial but woke folks up". Both athletes got a round of applause from the President, then vice-President Joe Biden, and the hundreds of athletes squeezed into the East Room of the White House.
When asked about living under Obama's successor President Donald Trump, Smith said: "You speak of politics and the last President - let's not go there now! It's a bit much for me especially. And those who are listening might say, 'Yeah, you're right Smith, it is a little big for you'!"
So, three years short of his 80th birthday, is Smith positive about the future?
"Well, gee whiz, you know, we're still here! So there's something good [that] is happening to what we are doing, and there's always going to be differences.
"To minimise our differences is going to take continual work. Nothing is forever and nothing is perfect. The younger generation must understand that you are the future. You have a general right to make, or it will be broken.
"Of course, I do believe it's worth it," Smith says without even a second of hesitation.
He believes he started "a new life" the moment he stepped off the podium.
Since those moments on October 16 in 1968 Smith has always maintained he did the right thing and talks about his "purpose".
"I think a lot of people, especially the younger generation, understood at that particular time. And now I guess it seems to me a rebirth of that stand because it's basically the same.
"This system still needs the understanding, the idea of getting along. Meaning you can see the difference in the colour. Of course everything has a colour. But in this particular human case, we have to work in spite of being black or being white or being brown.
"It is a colour of humanistic ideas or moving forward, being one instead of a bunch of absent-minded people who feel that they are better than other because of colour or because of money.
"You don't have to agree with what I say, but understand what I'm trying to bring forth, which is an understanding from the inside out.
"But I do believe that coming together, we have to see it as one. We have to see it as different colours come together, making the idea true that you don't have to be. But it is a fact that you have to understand.
"If you think Tommie Smith is negative I would say without a doubt you are wrong. I'm just a positive person who believed in talking, which I did not back in the time of my competitions.
"I let my actions do my talking. So later on, I could rectify my need to make known that love is the key. Understanding is the door and the background is the future of what you might be.
"I think we can see the light at the end of the tunnel.
"Right now it's still kind of blurry, but it's clearer now than it was in 68."
Sky Sports News presenter Mike Wedderburn reflects on the opportunity to interview Tommie Smith for Black History Month…
I was four years old when Tommie Smith stood on top of the podium in Mexico City in 1968 and with one black fisted glove took a swing at the world's racism.
As I grew up that iconic image of Tommie and John Carlos never seemed far away. Fast forward 53 years and I get a call, "Mike, we've lined up Tommie Smith for interview. Do you fancy it?"
Do I fancy it? Of course I fancy it! The opportunity to question a real life living legend doesn't come around every day.
Then there he is. Dr Tommie Smith sitting on the other end of a zoom call. He looked like he could still run the 200 metres in a decent time. His passion and energy undimmed over the intervening years.
One of the keys of good interviewing is to never get intimidated or star-struck by the person from whom you want answers. I finished the call by telling him that "I couldn't wait to tell my mum I'd spoken to Tommie Smith."
Click on the video at the top of the story to see Mike Wedderburn's full interview with Tommie Smith.