New on Sports Illustrated: This Day in Sports History: Rocky Marciano Retires From Boxing

Rocky Marciano retired at age 31 as the undefeated world heavyweight boxing.

Rocky Marciano holds one of the greatest records in boxing after ending his career early as an undefeated world heavyweight boxing champion at the age of 31. 

On April 27, 1956, Marciano and his manager, Al Weill, announced his retirement at a press conference at New York City's Hotel Shelton. Marciano, who went 49–0 with 43 KOs, said he wanted to retire to spend more time with his family. The sports world was stunned. Many boxers had retired only to later make comebacks, and people immediately wondered if Marciano would change his mind and eventually return to the ring. However, his mind was made up.

"I thought it was a mistake when Joe Louis tried a comeback. No man can say what he will do in the future. But, barring poverty, the ring has seen the last of me," Marciano said,

per The New York Times. "I am comfortably fixed, and I am not afraid of the future. Barring a complete and dire emergency, you will never see Rocky Marciano make a comeback."

Boxing had given Marciano a great life, as far as he was concerned. Born in Brockton, Mass., on September 1, 1923, Marciano grew up in a working-class family. He played baseball as a kid but took up boxing after he was drafted into the Army in 1943. Marciano continued his amateur boxing career after he left the military in 1946 and even tried out for a Chicago Cubs farm team. With his dreams of playing professional baseball dashed, Marciano became a pro boxer and defeated Lee Epperson in a third-round knockout on March 17, 1947.

Marciano was heavily criticized for his awkward boxing style and lack of footwork throughout his career. However, sportswriters respected his aggressiveness and the Italian-American community loved him. In October 1951, Marciano knocked out former heavyweight champion Joe Louis in eight rounds, joining the conversation as a potential contender. 

The "Brockton Blockbuster" was crowned champion when he knocked out Jersey Joe Walcott in Philadelphia on Sept. 23, 1952. The following year Marciano beat Walcott again in a first-round knockout in Chicago. Marciano defended his title five more times and defeated Archie Moore in September 1955 in what would become his final professional fight. 

Some people debate if Marciano's undefeated record is flawed and he won 49 bouts thanks to luck or mostly fighting guys that were past their prime. Despite the criticism, he retired as the only undefeated heavyweight champion in history. Thirteen years later, Marciano died in a plane crash in Iowa on Aug. 31, 1969.