It is exceedingly rare for one person to change the world almost single-handedly, but Justice Ruth Bader Ginsburg was one of those people. Even before her distinguished judicial career, RBG was a trailblazing advocate for women’s rights during the 1970s. She persuaded the Supreme Court that gender discrimination violates the Equal Protection Clause of the U.S. Constitution, winning five of the six cases she argued there. To lead this historic effort, RBG served as general counsel of the ACLU and as co-founder and the first director of its Women’s Rights Project from 1972 until she became a judge in 1980.How can we evaluate RBG’s performance in this role? If she had led a for-profit business, we could track its profits. But the test of a nonprofit’s success is not how much money it makes, but how much good it does in the world. To operationalize this somewhat abstract test, I have urged nonprofits to assess their work with three questions, which this Article applies to RBG’s impact litigation: First, how important was the problem RBG was trying to solve?Second, how effective was her response?Third, what were RBG’s comparative advantages in this work? To begin with the first question, RBG targeted an enormously significant problem. In the 1970s, gender discrimination had deep roots in U.S. law. Constantly encountering discrimination in her own career, RBG was emphatic that people should be judged by their ability, not their gender. Yet to advance this meritocratic vision, she had to change the way male judges thought about these issues.Second, how effective was RBG in pursuing this goal? She delivered extraordinary results, crafting a litigation strategy with three key strengths. First, instead of striving to accomplish all her goals in one case, RBG proceeded in stages, so that each new case built on the last one. Like a chess grandmaster, she thought several moves ahead. Second, RBG had a gift for seeing cases through the eyes of (skeptical) male judges, so she chose cases carefully, hunting for compelling facts. Third, ever mindful of her audience, she framed legal issues in ways that resonated with male judges.Along with targeting an important problem in an effective way, a nonprofit also should have comparative advantages in doing its work. This brings us to the third question: What were RBG’s unique strengths in leading the ACLU Women’s Rights Project? She had the courage to take controversial positions and the legal firepower to prevail. As both a successful professional and a devoted spouse and parent, RBG modeled her nonprofit’s mission in her own life. Yet although these issues were deeply personal for her, she rarely showed impatience or frustration. By temperament, RBG was unfailingly polite and collegial. She also knew that venting could set back her cause, and her goal was to do good, not to feel good. By combining this steely self-control with strategic thinking, determination, and eloquence, RBG was stunningly successful. In analyzing RBG’s record as a nonprofit leader, this Article draws not only on the historical record and RBG’s writings, but also on my own experiences with her. I served as her law clerk during the October Term 1994, her second year on the Supreme Court. Over the next twenty-five years, RBG was a generous mentor and a dear friend. We had countless conversations about her impact litigation.