Major League baseball has retired various uniform numbers in its history, ensuring that they will always be associated with one player of note. The numbers came into use 1929, when the New York Yankees and the Cleveland Indians began using them so fans and scorekeepers could tell who was who on the field. By 1937, each league demanded that all teams participate in the use of uniform numbers. The practice of retiring a number came with Lou Gehrig's retirement on January 6, 1940; his number 4 would never again be used by a Yankee player. Since then, over 120 other people have had their numbers retired.