As a columnist for Time magazine, among many other publications, Tom Callahan witnessed an extraordinary number of defining moments in American sport across four decades. He takes us from Roberto Clemente clinching his 3,000th, and final, regular-season hit in Pittsburgh; to ringside for the Muhammad Ali-George Foreman fight in Zaire; and to Arthur Ashe announcing, at a news conference, that he'd tested positive for HIV. There are also little-known...