On February 25, 1964, 22-year-old Cassius Clay shocks the odds-makers by dethroning world heavyweight boxing champ Sonny Liston in a seventh-round technical knockout. Former champ Joe Louis called it "the biggest upset in the history of boxing."

The dreaded Liston, who had twice demolished former champ Floyd Patterson in one round, was an 8-to-1 favorite. However, Clay predicted victory, boasting that he would “float like a butterfly, sting like a bee” and knock out Liston in the eighth round.

The fleet-footed and loquacious youngster who would later become known as Muhammed Ali needed less time to make good on his claim—Liston, complaining of an injured shoulder, failed to answer the seventh-round bell. A few moments later, a new heavyweight champion was proclaimed.

Cassius Marcellus Clay Jr. was born in Louisville, Kentucky, in 1942. He started boxing when he was 12 and by age 18 had amassed a record of over 100 wins in amateur competition. In 1959, he won the International Golden Gloves heavyweight title and in 1960 a gold medal in the light heavyweight category at the Summer Olympic Games in Rome. Clay turned professional after the Olympics and went undefeated in his first 19 bouts, earning him the right to challenge Sonny Liston, who had defeated Floyd Patterson in 1962 to win the heavyweight title.

On February 25, 1964, a crowd of 8,300 spectators gathered at the Convention Hall arena in Miami Beach to see if Cassius Clay, who was nicknamed the “Louisville Lip,” could put his money where his mouth was. The underdog proved no bragging fraud, and he danced and backpedaled away from Liston’s powerful swings while delivering quick and punishing jabs to Liston’s head. Liston hurt his shoulder in the first round, injuring some muscles as he swung for and missed his elusive target. By the time he decided to discontinue the bout between the sixth and seventh rounds, he and Clay were about equal in points. A few conjectured that Liston faked the injury and threw the fight, but there was no real evidence, such as a significant change in bidding odds just before the bout, to support this claim.

To celebrate winning the world heavyweight title, Clay went to a private party at a Miami hotel that was attended by his friend Malcolm X, an outspoken leader of the African American Muslim group known as the Nation of Islam. Two days later, a markedly more restrained Clay announced he was joining the Nation of Islam and defended the organization’s concept of racial segregation while speaking of the importance of the Muslim religion in his life. Later that year, Clay, who was the descendant of a formerly enslaved person, rejected the name originally given to his family by the owner of enslaved peoples and took the Muslim name of Muhammad Ali.

Muhammad Ali would go on to become one of the 20th century’s greatest sporting figures, as much for his social and political influence as his prowess in his chosen sport. After successfully defending his title nine times, it was stripped from him in 1967 after he refused induction into the U.S. Army on the grounds that he was a Muslim minister and therefore a conscientious objector. That year, he was sentenced to five years in prison for violating the Selective Service Act but was allowed to remain free as he appealed the decision. His popularity plummeted, but many across the world applauded his bold stand against the Vietnam War.

In 1970, he was allowed to return to the boxing ring, and the next year the U.S. Supreme Court overturned Ali’s draft evasion conviction. In 1974, he regained the heavyweight title in a match against George Foreman in Zaire and successfully defended it in a brutal 15-round contest against Joe Frazier in the Philippines in the following year. In 1978, he lost the title to Leon Spinks but later that year defeated Spinks in a rematch, making him the first boxer to win the heavyweight title three times. He retired in 1979 but returned to the ring twice in the early 1980s. In 1984, Ali was diagnosed with pugilistic Parkinson’s syndrome and has suffered a slow decline of his motor functions ever since. He was inducted into the International Boxing Hall of Fame in 1990. In 1996, he lit the Olympic flame at the opening ceremonies of the Summer Games in Atlanta, Georgia. Ali’s daughter, Laila, made her boxing debut in 1999.

At a White House ceremony in November 2005, Ali was awarded the Presidential Medal of Freedom. On June 3, 2016, Ali passed away after a period of failing health.