Muhammad Ali (; born Cassius Marcellus Clay Jr.; January 17, 1942 - June 3, 2016) was an American professional boxer and activist. He is widely regarded as one of the most significant and celebrated sports figures of the 20th century. From early in his career, Ali was known as an inspiring, controversial, and polarizing figure both inside and outside the ring. Cassius Clay was born and raised in Louisville, Kentucky, and began training as an amateur boxer when he was 12 years old.

Cassius Marcellus Clay Jr. () was born on January 17, 1942, in Louisville, Kentucky. He had a sister and four brothers. He was named for his father, Cassius Marcellus Clay Sr. (1912-1990), who himself was named in honor of the 19th-century Republican politician and staunch abolitionist, Cassius Marcellus Clay, also from the state of Kentucky. Clay's father's paternal grandparents were John Clay and Sallie Anne Clay; Clay's sister Eva claimed that Sallie was a native of Madagascar. He was a descendant of slaves of the antebellum South, and was predominantly of African descent, with smaller amounts of Irish and English heritage. His father painted billboards and signs, and his mother, Odessa O'Grady Clay (1917-1994), was a domestic helper. Although Cassius Sr. was a Methodist, he allowed Odessa to bring up both Cassius Jr. and his younger brother Rudolph "Rudy" Clay (later renamed Rahman Ali) as Baptists. Cassius Jr. attended Central High School in Louisville.  Clay grew up amid racial segregation. His mother recalled one occasion when he was denied a drink of water at a store--"They wouldn't give him one because of his color. That really affected him." He was also affected by the 1955 murder of Emmett Till, which led to young Clay and a friend's taking out their frustration by vandalizing a local railyard.  Clay was first directed toward boxing by Louisville police officer and boxing coach Joe E. Martin, who encountered the 12-year-old fuming over a thief's having taken his bicycle. He told the officer he was going to "whup" the thief. The officer told Clay he had better learn how to box first. Initially, Clay did not take up Martin's offer, but after seeing amateur boxers on a local television boxing program called Tomorrow's Champions, Clay was interested in the prospect of fighting. He then began to work with trainer Fred Stoner, whom he credits with giving him the "real training", eventually moulding "my style, my stamina and my system". For the last four years of Clay's amateur career he was trained by boxing cutman Chuck Bodak.  Clay made his amateur boxing debut in 1954 against local amateur boxer Ronnie O'Keefe. He won by split decision. He went on to win six Kentucky Golden Gloves titles, two national Golden Gloves titles, an Amateur Athletic Union national title, and the Light Heavyweight gold medal in the 1960 Summer Olympics in Rome. Clay's amateur record was 100 wins with five losses. Ali said in his 1975 autobiography that shortly after his return from the Rome Olympics, he threw his gold medal into the Ohio River after he and a friend were refused service at a "whites-only" restaurant and fought with a white gang. The story was later disputed, and several of Ali's friends, including Bundini Brown and photographer Howard Bingham, denied it. Brown told Sports Illustrated writer Mark Kram, "Honkies sure bought into that one!" Thomas Hauser's biography of Ali stated that Ali was refused service at the diner but that he lost his medal a year after he won it. Ali received a replacement medal at a basketball intermission during the 1996 Olympics in Atlanta, where he lit the torch to start the games.

Answer the following question by taking a quote from the article: where did he train
He then began to work with trainer Fred Stoner,