Norton was an outstanding athlete at Jacksonville High School. He was selected to the all-state team Football team on defense as a senior in 1960. His track coach entered him in eight events, and Norton placed first in seven of them. As a result, the "Ken Norton Rule", which limits participation of an athlete to a maximum of four track and field events, was instituted in Illinois high school sports.

'Name' opponents were elusive in Norton's early career. His first big break came with a clear win over respected contender Henry Clark. This helped get him his world recognition break when Ali agreed to a match. Joe Frazier, who'd sparred with Norton, presciently said of Ali, "He'll have plenty of trouble!" Though both were top boxers in the mid 1970s, Norton and Frazier never fought each other, in part because they shared the same trainer, Eddie Futch, and also that they were friends.  For the first match, on March 31, 1973, Muhammad Ali entered the ring at the San Diego Sports Arena wearing a robe given to him by Elvis Presley as a 5-1 favorite versus Ken Norton, then rated a number 6 world contender in a bout televised by ABC's Wide World of Sports. Norton won a 12-round split decision over Ali in his adopted hometown of San Diego to win the NABF heavyweight title. In this bout, Norton broke Ali's jaw (he maintains in round eleven, though Angelo Dundee said it was earlier), leading to only the second defeat for "The Greatest" in his career. (Ali's only previous loss was to Joe Frazier, and Ali would later go on to defeat George Foreman to regain the heavyweight title in 1974.)  Almost six months later at The Forum in Inglewood, California, on September 10, 1973, Ali avenged the Norton loss but only after he got the return by a split decision. Norton weighed in at 205 lbs (5 pounds lighter than his first match with Ali) and boxing scribes discussed that his preparation was too intense and that perhaps he had overtrained. There were some furious exchanges in this hard-fought battle. From Ali's point of view, a loss here would have seriously dented his claim of ever being "The Greatest." During the ABC broadcast of the fight, broadcaster (and Ali confidant and friend) Howard Cosell repeatedly told viewers a dancing and jabbing Ali was dominating the action despite Norton's constant offense and Ali's inability to penetrate Norton's awkward defensive style. The close and controversial scoring was in stark contrast to Cosell's fight-long insistence that Ali had matters well in hand.

What did Ali say in regards to Norton?