In April, Bruce Jenner spoke about her transition to woman in a television special that drew nearly 17 million viewers. On Monday, that woman revealed her new identity, appearing as Caitlyn Jenner on the cover of Vanity Fair. The photograph of Ms. Jenner in a revealing outfit, shot by Annie Leibovitz and accompanied by the headline “Call Me Caitlyn,” immediately became a sensation on social media when the magazine posted the article online. Ms. Jenner, 65, who won an Olympic gold medal in the decathlon, has had a long public life. As Bruce Jenner, she had been on the cover...