Muhammad Ali died Friday at age 74, according to a statement from the family. He was hospitalized in the Phoenix area with respiratory problems earlier this week, and his children had flown in from around the country. 

Throughout his professional career, he was known simply as "the greatest." Born Cassius Marcellus Clay in Louisville in January of 1942, he would win a gold medal in the 1960 Olympics in Rome. Four years later, he would fight Sonny Liston for the heavyweight title. Clay said he would float like butterfly and sting like a bee. The young 22-year-old would shock the world, winning by technical knockout when Liston failed to answer the bell in the seventh round.

"I feel great," Ali said. "I don't have a mark on my face and I upset Sonny Liston. And I just turned 22 years old. I must be the greatest I told the world. You took him in seven. I am the King of the World. Hold it. Hold it. I'm pretty. You're not that pretty. I'm a mad man. I took out the world. I took out the world."

Shortly after winning the world title, Clay joined the Nation of Islam and changed his name to Muhammad Ali.

In 1967, he refused to be drafted into the Army, citing his religious beliefs. He would eventually be found guilty of draft evasion and was stripped of his title. His appeal would go all the way to the Supreme Court and, in 1971, his conviction was overturned. Later that year, he fought Joe Frazier for the heavyweight crown at Madison Square Garden. It was dubbed the "Fight of the Century." Frazier decked Ali in the 15th, and Smokin' Joe won the fight by unanimous decision.

By 1974, George Foreman was the heavyweight champ and Ali met him in Zaire in "The Rumble in the Jungle." Ali regained the title with an eighth-round knockout. Following that, a third match with Frazier was set up. Ali had defeated Frazier in their second fight at the Garden. The third fight is famously known as the "Thrilla in Manila."

Ali was victorious a second time against Frazier. By the end of the 1970s, though, Ali's skills as a boxer were eroding. He lost fights to Leon Spinks and his former sparring partner, Larry Holmes. Before a fight with Holmes in 1980, Ali had begun to experience vocal stutters and trembling hands. Yet he was cleared to fight and was dominated by Holmes.

His final fight was against Trevor Berbick in 1981 in the Bahamas, a loss by decision in 10 rounds. In 1984, Ali was diagnosed with Parkinson's Disease. Some doctors feel it was brought on by the many blows to the head he suffered throughout his boxing career.

In his life after boxing, Ali was involved in charity work, political causes and in 1996, lit the Olympic flame in Atlanta.

In 2005, he was awarded the Presidential Medal of Freedom. His public appearances have been few and far between in recent years. He did attend the funeral of Joe Frazier in 2011 and was at the opening ceremonies of the London Olympics in 2012.

Ali had nine children and was married four times. His wife Lonnie was by his side since 1986. Muhammad Ali is gone, but will forever be remembered as the greatest.