Rocky Marciano retires as world heavyweight champion

On April 27, 1956, Heavyweight Champion, Rocky Marciano, retired undefeated from boxing. From the article:

Rocky Marciano retires as world heavyweight champion
On April 27, 1956, world heavyweight champ Rocky Marciano retires from boxing at age 31, saying he wants to spend more time with his family. Marciano ended his career as the only heavyweight champion with a perfect record–49 wins in 49 professional bouts, with 43 knockouts.

Rocco Francis Marchegiano was born into a working-class family in Brockton, Massachusetts, on September 1, 1923. After being drafted into the U.S. Army in 1943, he reportedly began boxing as a way to get out of kitchen duty and other less-than-desirable jobs. Marciano finished his military service in 1946 and continued to box as an amateur. He tried out for the Chicago Cubs, but his dream of becoming a pro baseball player ended when he was soon cut from the team. He returned to boxing and fought his first professional match on March 17, 1947, defeating Lee Epperson in a third-round knockout. Marciano went on to win his next 15 matches by knockout. He became known as a tough fighter and powerful puncher, but he was criticized for his awkward style, which some though lacked finesse.

On October 26, 1951, Marciano signaled to the boxing world that he was a contender when he faced former heavyweight champ Joe Louis and knocked him out in the eighth round. Marciano captured the heavyweight crown in Philadelphia on September 23, 1952, when he scored a knockout against defending champ Jersey Joe Walcott in the 13th round. Marciano faced Walcott again in Chicago on May 15, 1953, and defeated him in a first-round knockout. Marciano, nicknamed the “Brockton Blockbuster,” would successfully defend his title five more times, with his last professional bout, against Archie Moore in New York on September 21, 1955, ending in a ninth-round KO.

On April 27, 1956, Marciano announced his retirement from boxing and said he had no plans to return to the ring for a comeback. Marciano died in a small-plane crash in Iowa on August 31, 1969."