While studying at Yale, Rossiter once asked at the weekly informal gathering of her departments' professors and students "were there ever women scientists?". She received an "authoritative" reply that 'no, there were not, any such women who could be considered were just working for a male scientist', with one person referring to
Marie Curie as the only exception. This discovery spurred her Charles Warren Center fellowship talk,
Women scientists in America before 1920 which she published in the magazine
American Scientist after it was rejected by
Science and
Scientific American. The paper's success led her to continue her research in the area, despite a lukewarm reception from both the scientific and historical communities. She took a visiting professor position at
UC Berkeley where she prepared her dissertation for publication, and then she turned her attention to a new book on women scientists. Despite being told by some women scientists that "there was nothing to study," Rossiter found a wealth of information. She published her first volume,
Women Scientists in America, Struggles and Strategies to 1940, with
Johns Hopkins University Press in 1982. The book was well received, including positive reviews in
The New York Times,
Nature and
Science. After the publication of the first volume, Rossiter was asked to run the
National Science Foundation's (NSF) program on the History and Philosophy of Science while its director took a year of leave during 1982–1983. In 1983–1984 she was a visiting professor at Harvard, where she continued work on her second volume. Still unable to find a tenure-track position, she applied for the NSF's Visiting Professorships for Women program, and received a one-year appointment to Cornell, which she stretched to two years (1986–1988). Cornell agreed to keep her on for another three years, but her funding was split between three departments including women's studies, agriculture and history. The second volume was also well received, winning the
Women’s Prize and the
Pfizer Award, both from the
History of Science Society. The Women’s Prize was subsequently renamed the Margaret W. Rossiter History of Women in Science Prize, in honor of Rossiter; the vote on the renaming happened in 2004. She then became the Marie Underhill Noll Professor of History of Science Emerita and Graduate School Professor. Rossiter completed her trilogy on Women Scientists in America with the publication, in 2012 of
Women Scientists in American Volume 3: Forging a New World Since 1972. This last volume describes dozens of women who became advocates for the advancement of women in science after the passage of the
Equal Employment Opportunity Act of 1972, carrying to the present the story of Women in American Science. Rossiter's work has been especially significant as a framework for other scholars to build on. In the early 1980s, Margaret Rossiter offered two concepts for understanding the mass of statistics on women in science and the disadvantages women continued to suffer. The first she called hierarchical segregation, the well-known phenomenon that as one moves up the ladder of power and prestige fewer female faces are to be seen. This notion is perhaps more useful than that of the
glass ceiling, the supposedly invisible barrier that keeps women from rising to the top, because the notion of hierarchical disparities draws attention to the multiple stages at which women drop off as they attempt to climb academic or industrial ladders. The second concept she offered was "territorial segregation", how women cluster in scientific disciplines. The most striking example of occupational territoriality used to be that women stayed at home and men went out to work. Rossiter's work was commended by a woman scientist who noted having spent "a lot of money on psychotherapy because people kept telling me I was maladjusted". ==Death==