September 27, 1878 - June 3, 1955
Mary Sinclair was born in Worcester, Massachusetts, where her father, John Elbridge Sinclair, was professor of mathematics at Worchester Polytechnic Institute. She received her A.B. degree in 1900 from Oberlin College where she was inducted into Phi Beta Kappa, then studied at the University of Chicago, earning her master's degree in mathematics in 1903. From 1904 to 1907 she was an instructor at the University of Nebraska while continuing to work on her graduate studies in mathematics. She published two papers about surfaces of revolution in the Annals of Mathematics (Vol. 8, July 1907, and Vol. 9, July 1908). In 1908 Sinclair became the first woman to receive a Ph.D. in mathematics from the University of Chicago. Her dissertation in the calculus of variations, written under the direction of Oscar Bolza, was about "Concerning a Compound Discontinuous Solution in the Problem of the Surface of Revolution of Minimum Area." This was published in the Annals of Mathematics, Vol 10 (January 1909), pp55-80 [Abstract].
In 1907 Sinclair had returned to Oberlin College as an instructor in mathematics. She was promoted to associate professor upon receiving her Ph.D., and to full professor in 1925. In 1941 she was appointed Clark Professor of Mathematics at Oberlin College. Sinclair taught at Oberlin for 37 years, including being department chair from 1939 until her retirement in 1944.
Mary Sinclair never married. In 1914, however, she adopted an infant daughter, Margaret Emily. The following year she also adopted a son. She was on sabbatical leave during 1914-15 to care for her new family, and she also studied at Columbia and John Hopkins. During the 1922-1923 academic year, Sinclair pursued her mathematical research at the University of Chicago and Cornell University under the auspices of a Julia C. G. Piatt Fellowship from the American Association of University Women. Other sabbatical leaves were spent at the University of Rome and the Sorbonne (1925-26) and the Institute for Advanced Study (spring 1935).
After her's retirement in 1944, Sinclair taught part-time at Berea College in Kentucky before returning to live in Oberlin in 1947. She moved to Maine in 1953 where she died two years later. After her death, the Journal of the American Association of University Women, in writing about Sinclair's generous gift to the AAUP to support the Fellowship Fund that had provided her "the best period of creative scholarship in my life," remarked that:
Modest and selfless, she never became an "ivory tower" scholar. Rather, she sought to infect other students with the spark that finds in creative research one of the world's greatest challenges. In her teaching, she shared the spark; with her gift, she opened up a path to research for others.