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I'll add George Ruth, Harold Grange, perhaps Ali, Shorter + by SixShutouts66
Mary Lou Retton, Jackie Robinson, Pele, Richard Petty, Mia Hamm, Fernando Valenzuela
Babe Ruth is pretty obvious in ushering in the Golden Age
Red Grange was a very well known football player, even legendary, before he boosted the fledgling NFL
Ali gave a boost to a dying sport and was its face for many years
Frank Shorter had a gold and silver in the Olympic marathon at the time road racing took off in the US. Not sure if his victories contributed to it or just occurred at the same time
Mary Lou Retton made the Cheerios package and was one of the first successful American gymnasts
Jackie Robinson and others (Sweetwater Clifton, Marion Motley) broke racial barriers
Pele was a marquee star in soccer when most Americans had minimal experience with it and he filled seats
Richard Petty seemed to be the most recognizable NASCAR star when it grew from a regional sport
I might make a case for Mia Hamm and Fernando Valenzuela - Fernando certainly exploded in Los Angeles, especially among the Hispanic folks