Before a preseason game on September 1, 2016, San Francisco 49ers quarterback Colin Kaepernick knelt during the national anthem to call attention to issues of racial inequality and police brutality—a protest that continues to stir intense debate. For decades, American athletes have used their platforms for protests. Here are some of the more notable examples.

During the 1995-96 NBA season, the Denver Nuggets' star refused to stand for the national anthem, declaring it would be a violation of his Muslim faith. Mahmoud Abdul-Rauf told reporters the American flag was “a symbol of oppression, of tyranny.” The NBA suspended him for one game before reaching a compromise—Abdul-Rauf would stand and pray during the anthem. But Abdul-Rauf paid a price for his stance: Denver traded him to Sacramento after the season, and despite his prolific scoring, he was out of the NBA by age 29.

When he and four of his Black teammates on the Boston Celtics were refused service in a restaurant in Lexington, Kentucky, Bill Russell told coach Red Auerbach they wouldn't play in an exhibition game in the city. Two members of the St. Louis Hawks, Boston's opponent, joined them in the boycott. Auerbach didn’t exactly stick up for his players, telling the Associated Press, “The Negro boys got real emotional. They said they’d like to go home. We talked for two hours, and I couldn’t change their minds.”

Russell and his teammates flew back to Boston, where the star declared: “Negroes are in a fight for their rights, a fight for survival in a changing world. I am with these Negroes." A day later, Celtics owner Walter A. Brown told the Boston Globe the Celtics wouldn’t play games in the South again, adding, “I’m not so hungry for money that I’d arrange games that might embarrass my players.” At the time, the league consisted of only nine teams.

The AFL All-Star Game in New Orleans was a nightmare for the Black All-Stars. Taxis refused to pick up Black players, nightclubs on Bourbon Street were segregated, and a bouncer pulled a gun on tackle Ernie Ladd. After that, the players refused to play. New Orleans Mayor Victor Schiro told the Associated Press the protest would “aggravate the very condition they are seeking, in time, to eliminate.”

But AFL commissioner Joe Foss didn't blame the players for withdrawing, and he quickly relocated the game to Houston. The protest accelerated the desegregation of New Orleans, as business owners feared the financial losses from missing out on big sports events.

When the U.S. Army said Muhammad Ali was draft-eligible, he declared he was a conscientious objector to military service, as the war was against his Muslim faith. “I ain’t got no quarrel with them Viet Cong,” he told reporters. On April 28, 1967, Ali refused induction into the army, and was stripped of his heavyweight titles and banned from boxing for three years.

Two months later, Ali was convicted by an all-white jury and sentenced to five years in prison for his refusal. Public opinion was against him, with the Atlanta Constitution claiming: “Clay has plenty of company in the draft-dodging league.” (At the time, few in the media referred to him as Muhammad Ali.) Four years later, however, the Supreme Court reversed Ali’s conviction in a unanimous vote. Ali, one of the greatest athletes of all time, retired from boxing in 1981.

Tommy Smith won a gold medal and John Carlos the bronze in the 200 meters in Mexico City, but history remembers what they did on the medal podium. While the "Star-Spangled Banner" played, each man raised a black-gloved fist—a Black Power salute. All three athletes on the podium wore human rights badges, including the Australian silver medalist, Peter Norman.

International Olympic Committee President Avery Brundage immediately banned Smith and Carlos, who were vilified in the media—Brent Musburger, then a Chicago sports writer, called them “a couple of black-skinned storm troopers.” Neither Smith nor Carlos won another medal at the Olympics. Decades later, Smith said the medal-stand protest was in support of human rights.

Wyoming’s football team was undefeated and ranked 12th the week of its game against Brigham Young University. But when 14 Black members of the team visited head coach Lloyd Eaton to discuss an upcoming protest of the allegedly racist policies of the Mormon Church, Eaton shut them down. "Gentlemen, you can save time and breath," he said, according to one of the Black players. "As of now, you're off the football team.”

A week later, four Black track athletes at Wyoming quit in solidarity with the football players, and the football team was met by protests at every road game. In their next 38 games after the mass dismissal, the Cowboys won only 12; Eaton was out as coach after the 1970 season. In 2019, the university apologized to the “Black 14.”

After the Open Era in tennis began in 1968, men earned far more prize money than women. Billie Jean King decided to fight, boycotting a 1970 tournament because it awarded men $12,500 and women only $1,500. King arranged a rival tour, despite facing suspension from the U.S. Lawn Tennis Association.

By September 1970, tournaments increased purses for women to avoid boycotts from King and her like-minded competitors, In June 1973, King became the first president of the Women’s Tennis Association. A month later, the U.S. Open announced men and women would receive equal prize money.

Nine Black players boycotted spring practice to protest the lack of Black assistants or access to the same academic and medical resources as white players. Also, Syracuse wouldn’t take Black players to road games in southern cities. White teammates threatened to quit if they were reinstated, with linebacker Bill Coghill telling the Associated Press: “I don’t care if you call me a bigot. I’m not going to take it.” The Black players sat out the entire season, derailing their football careers, though all nine student-athletes graduated.