In a book released last year, The Secret History of Wonder Woman (Knopf 2014), Harvard historian and New Yorker staff writer Jill Lepore explores the connection between Wonder Woman and Margaret Sanger. Through impeccable historical analysis and detection, she shows us that the most well-known comic icon of 1940s feminism was actually largely inspired by another feminist icon of the first half of the twentieth century: Margaret Sanger.

In doing research for this book, Lepore uncovered a never-before-seen collection of documents, including William Moulton Marston’s private documents. She discovered that in creating Wonder Woman, Marston was profoundly influenced by early twentieth century suffragists, feminists, and birth control advocates, including Margaret Sanger, who was secretly a member of his family.

Dr. William Moulton Marston, creator of Wonder Woman

Marston entered Harvard College as a freshman in 1911, the same year that Emmeline Pankhurst was barred from speaking on campus and gave a fiery speech in Harvard Square instead. He married Elizabeth Holloway, a feminist alumna Mount Holyoke, in 1915. He received a law degree and a PhD in Psychology from Harvard, and she from Boston University and Radcliffe, and they launched their academic careers in psychology. In 1925, while teaching at Tufts, Marston fell in love with one of his students, Olive Byrne: Ethel Byrne’s daughter and Margaret Sanger’s niece.

In 1926, Olive Byrne moved in with Marston and Hollaway; they lived as a threesome, with, in Holloway’s words, “love-making for all.” Byrne is the mother of two of Marston’s four children, and Holloway the mother of the other two. The children effectively had three parents. This domestic set-up was no doubt unconventional, and it cost him his academic career.

Marston, center, surrounded by his unconventional family.

In 1928, it became clear to Marston that his academic career was doomed, so he began a career in the burgeoning industry of cinema. However, he was not as successful as he would have hoped, and he spent most of the 1930s unemployed, supported by Holloway who worked for Met Life insurance, while Byrne raised the children. The unconventional family maintained close ties with Byrne’s aunt, Margaret Sanger, who was rather unfazed by the “family intrigue.”

In 1937, the year the American Medical Association finally endorsed contraception, Marston held a press conference in which he predicted that women would one day rule the world. He also offered a list, “in the order of the importance of their contributions to humanity,” of six surpassingly happy and influential people: Margaret Sanger was No. 2, just after Henry Ford and just before F.D.R. The story was picked up by the Associated Press, wired across the continent, and printed in newspapers from Topeka to Tallahassee. “Women Will Rule 1,000 Years Hence!” the Chicago Tribune announced. The Los Angeles Times reported, “FEMININE RULE DECLARED FACT.”

In 1940, Marston was hired by M.C. Gaines, who published Superman, as a consultant. He convinced him that the Justice Society of America needed a female superhero. Thus, Wonder Woman debuted in 1941. A press release explained, “ ‘Wonder Woman’ was conceived by Dr. Marston to set up a standard among children and young people of strong, free, courageous womanhood; to combat the idea that women are inferior to men, and to inspire girls to self-confidence and achievement in athletics, occupations and professions monopolized by men” because “the only hope for civilization is the greater freedom, development and equality of women in all fields of human activity.” Marston put it this way: “Frankly, Wonder Woman is psychological propaganda for the new type of woman who should, I believe, rule the world.” And as shown by his list of influential people, Margaret Sanger was just that type of woman.

For a reason unbeknownst to the author, Margaret Sanger wanted to keep well-hidden her ties to the comic-book superhero created by Marston. Maybe it was because she found the association embarrassing, or because she wanted to keep Olive Byrne’s family situation a secret. Whatever the reason, Margaret Sanger never mentioned Wonder Woman.

Marston died suddenly in 1947, but Holloway and Byrne stayed together for the rest of their lives, taking care of Sanger in her old age in Tucson. In 1965, when the Supreme Court effectively legalized contraception, in Griswold v. Connecticut, Byrne wrote to Justice William O. Douglas, who had written the opinion for the 7-2 majority, “I am sure Mrs. Sanger, who is very ill, would rejoice in this pronouncement which crowns her 50 years of dedication to the liberation of women.” Sanger died the next year.