Which Major League Baseball (MLB) player was the first to have his number retired?

Major League Baseball (MLB) and its participating clubs have retired various uniform numbers over the course of time, ensuring that those numbers are never worn again and thus will always be associated with particular players or managers of note. The use of numbers on uniforms is to better identify one player from another, and hence to boost sales of scorecards, was tried briefly by the Cleveland Indians of 1916. The first team to permanently adopt the practice was the New York Yankees of 1929. By 1932, all 16 major league clubs were issuing numbers, and by 1937, the leagues passed rules requiring it.

The Yankees' original approach was to simply assign numbers 1 through 8 to the regular starting lineup in their normal batting order. Babe Ruth wore number 3 and Lou Gehrig number 4. The first major leaguer whose number was retired was Gehrig, in July 1939, following his retirement due to amyotrophic lateral sclerosis (ALS), which became known popularly as Lou Gehrig's Disease.

Since then, over 150 other people have had their numbers retired, some with more than one team. This includes managers and coaches, as Major League Baseball is the only one of the major North American professional leagues in which the coaching staff wear the same uniforms as players.