In 1916, Margaret Sanger opened a birth-control clinic in Brooklyn, New York, marking the first major endeavor of her career in social activism, which culminated in 1942 when she founded Planned Parenthood. Contrary to what many might assume from witnessing Planned Parenthood operate today as the nation’s largest abortion business, Sanger wasn’t an abortion activist.

Instead, she founded Planned Parenthood as part of a crusade for contraception, which she believed would be an important element of social progress. Unlike feminists later in the 20th century who demanded birth control as a means of liberating women from the supposed tyranny of the female body, Sanger and her allies had a more nefarious angle.

It was the Progressive Era, and elite progressive leaders were advocating a frightening campaign: Anglo-Saxon–oriented eugenic policy as a means of reshaping the U.S. population to look, in their view, more ideally American.

In her 1919 essay “Birth Control and Racial Betterment,” Sanger couched her argument for birth control in the context and aims of the eugenics movement. “Elimination of the unfit,” Sanger argued, could not be fully achieved without widespread access to birth control.

Sanger later elaborated on what she meant by “unfit,” describing the link as she saw it between birth control and progress: “If we are to develop in America a new race with a racial soul, we must keep the birth rate within the scope of our ability to understand as well as to educate. We must not encourage reproduction beyond our capacity to assimilate our numbers so as to make the coming generation into such physically fit, mentally capable, socially alert individuals as are the ideal of a democracy.”