In late December, Focus Features released On the Basis of Sex, a biopic about Supreme Court Justice Ruth Bader Ginsburg. Starring Felicity Jones, On the Basis of Sex highlights Ginsburg’s journey through law school, her teaching career, and her family relationships, particularly with her husband, Martin, and her daughter, Jane. The film shows the challenges Ginsburg faced as a woman pursuing a legal career in the mid-twentieth century and how she began to fight sex discrimination.

Although not a full portrait, the film offers a fascinating glimpse into Ginsburg’s early life, beginning with Ginsburg’s arrival at Harvard. Significantly, the film includes the dinner for new female law students, where the Dean of Harvard Law customarily asked women why they were taking a spot that could have gone to a man. It’s an uncomfortable, frustrating moment in the film and only the first of many. The motivations behind this question may run deeper; in her new biography of Justice Ginsburg, historian Jane Sharron de Hart explains that Dean Griswold asked the question to elicit proof that women should attend Harvard Law, something for which he had fought. As the film shows, Ginsburg’s law school and early career experiences influenced her fight against sex discrimination.

Ginsburg’s first sex discrimination case, Moritz v. Commissioner of Internal Revenue (1972), targeted the U.S. tax code. Charles Moritz, a never-married man from Colorado, claimed a caregiver expenses deduction after hiring a caregiver for his elderly mother. Moritz hired a caregiver because he worked full time, but was denied the tax deduction because it was only available for women, widowed or divorced men, or a married man whose wife was “incapacitated or institutionalized”On the Basis of Sex shows how Ginsburg and her husband successfully argued their case in the 10th Circuit Court. Moritz got his deduction and the IRS rewrote their law.

Following Moritz’s success, Ginsburg and the American Civil Liberties Union (ACLU) formed the Women’s Rights Project and Ginsburg went on to argue several significant cases. Ginsburg’s next case brought her before the Supreme Court for the first time and became a landmark ruling that revised more than two decades of discriminatory military law.

Frontiero v. Richardson (1973) centered on Air Force Lieutenant Sharron Frontiero’s fight to obtain dependent benefits for her civilian husband. Had Frontiero been a serviceman married to a woman, the civilian spouse would have gotten benefits – such as housing allowance and medical benefits – automatically. However, civilian husbands only received these benefits if they were dependent on their wives for at least one-half of their support.

The law’s genesis dates to the 1948 Women’s Armed Services Integration Act, which authorized women’s permanent military service. Nurses had achieved the same status in the early twentieth century, and women outside of the nursing profession served in both world wars temporarily. Although the numbers of servicewomen in the Army, Navy, Air Force, and Marines remained small in the next three decades, military service became a career path in which women challenged sex discrimination before the rise of second wave feminism.

Significantly, the Women’s Armed Services Integration Act offered women equal pay and benefits with men in a time when such equity was generally unavailable. In 1948, legislators believed they offered women equality with men because servicewomen would fill almost any role a man could, except combat, which became defined as a category of service available to men only; military leaders saw no contradiction in identifying women as equal with servicemen while barring them from combat. What military leaders and legislators believed for several decades was that equality meant allowing women to serve any role they were capable – but their sense of women’s capability derived from assumptions about what women should be and do.

Consequently, the law was riddled with contradictions. Believing that women should never lead men, rank limitations kept women from advancing beyond permanent ranks of lieutenant colonel or captain. No one envisioned a female general or admiral in 1948; the law remained unchanged until 1967. Officials discharged new mothers automatically. And, as noted, servicewomen’s spouses were largely excluded from family benefits that military wives received. These limitations and many other practices (often related to utilizing women in traditionally feminine jobs) undermined the idea that men and women were equal partners in defense.

Sharron Frontiero was not the first to challenge policies related to servicewomen’s family members, but due in part to Ruth Bader Ginsburg, Frontiero became the first to successfully change long-standing laws.

In January 1973, nearly a year after the Equal Rights Amendment passed in Congress, Ginsburg joined Frontiero’s attorney at the Supreme Court. Ginsburg acted as an amicus curiae (friend of the court) with ACLU, to focus on strict scrutiny and gender discrimination. This was not the first time the justices had heard sex discrimination arguments – Reed v. Reed in 1971 had done that. Ginsburg’s brought new depth to the fight against gender discrimination, in this case addressing the stereotype, as Ginsburg put it, that “man is or should be the independent partner in a martial unit. The woman with an occasional exception is dependent, sheltered from bread winning experience.”

Ginsburg argued that the law discriminated against women on the basis of sex because all servicemen received dependent benefits for civilian wives, but civilian husbands could do so rarely. The law set what looked like financial criteria for civilian husbands to receive benefits, but differentiated by sex due to assumptions about gender roles.

Ginsburg particularly fought to make sex a suspect classification and to have strict scrutiny applied. “Sex,” Ginsburg argued, “like race is a visible, immutable characteristic bearing no necessary relationship to ability.” Both sex and race, she continued, have historically been “the basis for unjustified or at least unproved assumptions concerning an individual’s potential to perform or to contribute to society.” Ginsburg wanted the justices to recognize this problem: just because Americans have many assumptions about men’s and women’s roles did not mean they should be limited to those assumptions by law. If the Supreme Court made sex a suspect classification, as race was, courts nationwide would have better guidance to respond to gender discrimination, rather than remaining divided in their responses to sex discrimination.

Ginsburg particularly countered the claim that suspect classification was not applicable for sex because women are a majority of the population. She emphasized that looking at numbers alone overlooked larger realities: sex discrimination in employment, educational quotas, and, importantly, the absence of women in government. While there might be many laws regarding women and intended to protect women, the lack of women in law-making positions at all levels meant women had a limited role in making laws. Thus, even laws designed to protect women had been created largely by men acting on assumptions about women’s proper roles. As she also reminded the justices, even though women were a majority, it still took nearly 150 years after the signing of the Declaration of Independence for women to secure the right to vote.

Ginsburg explained that creating laws that used sex to create different standards for men and women had important historical impact. For example, in Mueller v. Oregon (1908), sex had been used to limit women’s work hours – but not men’s. By the 1970s, however, those same laws prevented women “from competing for extra remuneration, higher paying jobs, promotions.”

That same criteria also created harm for women by assuming women had better things to do than participate as citizens. “The sex criterion stigmatizes when, as in Hoyt v. Florida 368 U.S, it assumes that all women are preoccupied with home and children and therefore should be spared the basic civic responsibility of serving on a jury.” Such laws had been intended to protect women, but did something worse, Ginsburg maintained. “These distinctions help keep women in her place, a place inferior to that occupied by men in our society.”

According to Ginsburg, to change that reality – a nation where legally-codified gender assumptions kept women in a specific place – the law must be changed, and the courts must recognize sex as a suspect classification requiring strict scrutiny. Frontiero was a particularly significant case for making this argument because the armed forces were a place that purported to give men and women some degree of equality – equal pay based on rank, the opportunity for women to fill a wider range of jobs than they might in the civilian world, and perhaps even some of the most opportunities for men and women to work side by side. In an environment like that, Ginsburg pointed out, any legislation that distinguished between supposed equals, such as the benefits law, was especially problematic. “Legislation making a distinction, servicewomen regard as the most frozen equity, the greatest irritant and the most discriminatory provision relating to women in the middle — in the military service.”

Ginsburg concluded her arguments with a connection to Sarah Grimke, an antebellum abolitionist and “advocate of equal rights for men and women”: “I ask no favor for my sex. All I ask of our brethren is that they take their feet off our necks.” Sharron Frontiero asked no special treatment, but only the same as any other married service member. By denying her and her spouse dependent benefits, the U.S. government kept their feet on her neck, preventing her from serving her nation as she hoped.

Sharron Frontiero won her case: the law changed, and in the 1970s military women began to see their equality expand. Three years later, women entered the service academies. Mothers gained the ability to remain in service. By the end of the decade, even the administrative structures established for military women disappeared, with women and men becoming more fully integrated in the military.

Despite what military officials claimed, equal pay and permanent status in the armed forces did not make servicewomen equal to men. In 1973, Ruth Bader Ginsburg became part of a larger evolution in defining equality for women in the armed forces and helped make servicewomen more equal with her arguments in Frontiero.

The question of what it means for American servicewomen to be equal with servicemen continues today, but has evolved from a question of benefit equity to one that hinges on women’s ability to participate in any military function, including combat.

Yet as Sharron Frontiero’s case demonstrates, simply including women into the armed forces in the twentieth century was not enough to make women equal. Admitting women to all areas of military service, based on physical capability rather than assumptions of women’s abilities has improved sex equality in the military, but not realized it. As women’s military opportunities expand, our understanding of what it means for servicewomen and men to be equal evolves as well.

Ruth Bader Ginsburg’s work has undone many instances of sex discrimination in American law. Her work led to greater awareness of sex discrimination and new challenges to such discrimination. On the Basis of Sex, makes clear that American culture and law have moved forward so much in half a century due, in large part, to her efforts. It may be tempting, even, to think that the problems have been solved. The other message of On the Basis of Sex lies in the history Ginsburg considers as she makes her case in Moritz and Frontiero: as culture changes, law changes, and vice versa. Our definition of equality and the importance of equality between the sexes has evolved in ways not foreseen a century or even half a century ago. New assumptions about men and women, and new gender identities, have emerged. Ginsburg’s work is unfinished, but continues, as importantly as ever.

Tanya L. Roth completed her PhD in American history at Washington University in St. Louis. She is writing her first book manuscript, Flirting with Equality: American Women in the Cold War Military , which examines the evolution of women’s military service and changing definitions of equality in the armed forces. Tanya teaches high school history at Mary Institute and St. Louis Country Day School in St. Louis, MO.