Peggy Fleming, for elevating the artistry of free skating and Janet Lynn, for making free skating the "main event."
Interestingly, Peggy Fleming, who was very graceful and a good jumper, was also good at school figures. In fact, if I recall correctly, it was the school figures section of her skating that put her ahead at the 1968 Olympics, and it kept her ahead even though she skated conservatively in her free program. So Peggy was really an all-around skater at a time when that description had to include school figures. Janet Lynn, on the other hand, was strong in free skating (both artistically and in terms of jumps) but generally faltered in school figures. These two ladies did a lot to usher in the era of artistic ladies' skating. They were a kind of one-two punch: Peggy's era of dominance was from about 1965 to 1968 (three World championships and then the OGM), and then Janet took center stage in the U.S., though she never won a World or Olympic gold medal. Her most immediate rivals were Trixi Schuba and Canada's Karen Magnussen, who won the World Championship in 1973 when Janet fell. (Magnussen was also the Olympic silver medalist in 1972, behind Schuba and ahead of Lynn.)
I feel that had the plane crash that killed the 1961 American team not happened, the change in ladies' skating would have happened earlier, because Laurence Owen seems to have had that quality of grace plus athleticism that might have turned the tide then. I am too young to have seen her live, but there are one or two YouTube videos available, and no less a voice than Toller Cranston thought very highly of her skating.