Happy birthday, Muhammad Ali! The boxing legend and renowned social activist turns 72 today. Born Cassius Clay in Louisville, Ky., he rose to international fame after upsetting Sonny Liston for the heavyweight championship in 1964. Shortly after, he joined the Nation of Islam and changed his name. Because of his religious beliefs and opposition to the Vietnam War, Ali refused to join the United States military in 1967. He was arrested and found guilty of draft evasion and was subsequently stripped of his boxing title. Ali appealed the conviction and it was finally overturned in 1971 by the U.S. Supreme Court. During his years fighting for his innocence, and not opponents in the ring, he became an icon for the anti-war and civil-rights movements. “The Greatest,” as he is nicknamed, returned to boxing and reclaimed his heavyweight title in 1974 and again 1978. He retired from the sport in 1981 and was diagnosed with Parkinson’s Disease three years later. Ali is hte father of nine children, including daughter Laila who followed in his boxing footsteps. He has continued to work for social justice through his own center and with other projects. He was presented with the Presidential Medal of Freedom in 2005.