ONE HUNDRED YEARS AGO THIS OCTOBER, Margaret Sanger opened the first family-planning clinic in the United States. During its first 10 days, Sanger and her younger sister, nurse Ethel Byrne, offered clinical visits and information to the women in the Brownsville neighborhood of Brooklyn—home to thousands of Jewish and Italian immigrants. Their aim was to help them avoid getting pregnant.

On the eleventh day an undercover policewoman arrived, with a borrowed baby in her arms. Based on what she saw, she had Sanger arrested and the clinic shut down. It was illegal to provide information about contraception unless a physician offered it to “cure or prevent disease.” Though Sanger had sought such a physician to help her open the Brownsville clinic, no one had been willing to sign on.

The short-lived Brownsville clinic was a milestone in the history of contraceptive medicines and devices. Methods to forestall pregnancy and end early pregnancy are among the earliest treatments on record, appearing in documents that go back more than 3,000 years. But while the nineteenth century saw radical improvements in almost every area of medicine, birth control remained not only a taboo field but often an illegal one.

When Sanger began her work, the most popular methods included condoms, douches and, for wealthy patients privy to discreet medical information, fitted barriers called pessaries—small caps made of rubber and other materials that could be placed against the cervix and treated with spermicides. These products were sold under the auspices of “feminine hygiene” or “marriage hygiene.” Spermicidal suppositories were available as well. But many physicians, wary of this shadow industry, recommended coitus interruptus and the rhythm method to patients who asked how to forestall pregnancy.

The pessary struck Sanger as the safest and most effective approach, and the one most firmly under a woman’s control. She had seen pessaries during a visit to the Netherlands, where she spent two months of a yearlong self-imposed exile while on the lam from U.S. authorities. (A magazine she published about contraception, The Woman Rebel, had led to her arrest after it was deemed “obscene, lewd, lascivious, filthy and of indecent character.”) The Dutch pessary came in 14 sizes and needed to be fitted by a physician. Dutch studies in contraception showed that the devices had a failure rate of only 1%. In the United States, some pharmacies sold the devices to treat uterine prolapse following pregnancy. Sanger’s proposal to make these the cornerstone of her birth control movement was an early example of off-label use of medical drugs and devices.

In the back room of her Brownsville clinic, Sanger and her sister fitted pessaries and taught patients how to use them. They also gave information about spermicides and instructions for making them at home, providing various formulas that featured boric acid, quinine, bichloride, vinegar or other easily available ingredients.

Sanger became a champion of the pessary and its evolution. After seeing spring-loaded diaphragms—a German twist on the pessary dating back to 1882—she began smuggling them into the United States in large quantities with the help of her wealthy second husband, the 3-in-One Oil magnate Noah Slee. The couple would later invest in the first diaphragm manufacturing company in the U.S.

In 1923, Sanger launched the Clinical Research Bureau, later renamed the Birth Control Clinical Research Bureau, to address the dearth of reliable studies about the performance of the birth control drugs and devices. She enlisted Hannah Stone, a pediatrician, to be the clinic’s director. Stone would go on to use the records of 100,000 patients she saw at the clinic to evaluate the safety and effectiveness of the diaphragm. Her early findings, that the device caused few long-term effects, were published in 1928, one of the first reports on birth control to appear in a medical journal.

While advocates continued to lobby Congress for a doctor’s right to prescribe birth control, Sanger’s more confrontational tactics finally broke the ice. She asked Stone to order a shipment of 120 pessaries from Japan, then informed the U.S. Customs Office of their imminent arrival. The subsequent seizure of the package led to a court case in 1936. The judge ruled that the law should not prevent the importation or sale of items that could be intelligently used by doctors to promote the well-being of their patients. Physicians in New York were given the authority to prescribe birth control devices as they deemed fit and were permitted to send or receive contraceptives across state lines. But it would be more than 30 years before the federal government officially removed all other legal prohibitions against them.

Until her death, Sanger continued to push for better, safer devices for contraception. At age 73, she acted on her longtime desire to create “some sort of pill” that would offer even more continuous and infallible contraception. Along with her friend Katharine McCormick, an heiress to the International Harvester fortune who provided much-needed funding, she worked with Massachusetts researchers Gregory Pincus, Min Chueh Chang, and John Rock to create what would become Enovid in 1957. It was the first oral contraceptive. Pincus had long studied the role of progesterone in mammalian pregnancies, and their pill would contain a synthetic version of progesterone that mimicked a pregnancy and halted ovulation.

In Massachusetts, distributing information about birth control could still result in jail time. So Rock and Pincus administered Enovid in trials to women at Worcester State Hospital under the auspices of an investigation of menstrual disorders and infertility. They also administered trials in Puerto Rico, a territory that had been far more progressive than the mainland about contraception. Enovid was first approved as a drug for regulating menstrual cycles, and only in 1960 was cleared for expanded labeling as a contraceptive.

Sanger’s name today is closely identified with Planned Parenthood, which came out of two organizations that Sanger founded early in her career. Although the organization is still at the center of political firestorms—the clinics have recently been stripped of funds by 10 state legislatures and are under threat of defunding by others—Planned Parenthood continues Sanger’s work, not only in offering expanded access to birth control, but in pushing medical innovation. Most recently, the group began the use of telehealth in five states to prescribe birth control to remote patients.

While Sanger’s place in history as a cultural crusader is well deserved, on the centenary of her first clinic, it should be remembered that she was also a medical innovator, pushing the use and development of better, healthier treatments for women.