Stephanie Trevor was born in February, 1953. Her mother Diana Trevor went to labor at the same time as Lois Lane Kent. Thus Stephanie was born the same day as Kara Kent. Her father, General Steve Trevor had been recently reported MIA in the Korean War. An investigation by then then-acting Wonder Girl revealed that he was actually dead, another casualty of the War.

By 1964, eleven-year-old Stephanie Trevor had started operating as the new Wonder Girl. Keeping her superhero activities secret from her mother. At one prominent adventure, Stephanie had to help fellow heroes Kid Flash/Wallace West, Robin/Bruce Wayne Jr, Supergirl/Kara Kent against an alliance of Gorilla Grodd, Mirror Master, and Weather Wizard. The four heroes won that day and decided to form a new team: the Justice League of America.

By 1986, Stephanie was acting as the new Wonder Woman. She used to have a psychic link with her close friend Supergirl/Kara Kent. A bond severed when Kara was murdered. That year, Stephanie had to team-up with Green Lantern/Alan Scott and Flash/Carrie Allen in an unusual mission. They had to capture an unhinged Batman/Bruce Wayne Jr. Bruce's mental state was the widower of Kara and his mental state was fragile for years.