Blanch was born Gittel Kaimowitz in Kolno, Poland, arrived in the United States as a child, and attended public schools in New York City. She spent fourteen years as a clerk, saving money for school. She received a Bachelor of Science degree in Mathematics with a minor in Physics from New York University in 1932. She received her Ph.D. from Cornell University in algebraic geometry in 1935.
For a while she worked as a substitute teacher at Hunter College; then, in 1938, she began work on the Mathematical Tables Project of the WPA, for which she was "Director of Mathematics" and "Manager of Computation." This entailed designing algorithms that were executed by teams of human computers under her direction. Many of these computers possessed only rudimentary mathematical skills, but the algorithms and error checking in the Mathematical Tables Project were sufficiently well designed that their output defined the standard for transcendental function solution for decades. This project later became the Computation Laboratory of the National Bureau of Standards.
The Mathematical Tables Project became an independent organization following the termination of the WPA at the end of 1942. During World War II, it operated as a major computing office for the US government and did calculations for the Office for Scientific Research and Development, the Army, the Navy, the Manhattan Project and other institutions. Blanch led the group throughout the war.
After the war, Blanch's career was hampered by FBI suspicions that she was secretly a communist. Their evidence for this seems scarce, and included, for example, the observation that she had never married or had children. In what must have been a remarkable showdown, the diminutive fifty-year-old mathematician demanded, and won, a hearing to clear her name.
She published over thirty papers on functional approximation, numerical analysis and Mathieu functions. In 1962, she was elected a Fellow in the American Association for the Advancement of Science. In 1964, she received the Federal Woman's Award, an award for women who had exemplary professional service in the United States Government.
Blanch retired in 1967 at the age of 69, but continued working under a consulting contract for the Air Force for another year. Thereafter she moved to San Diego and continued to work on numerical solutions of Mathieu functions until her death in 1996, concentrating on the use of continued fractions to achieve highly accurate results in a small number of computational steps. This work has not been published.
Note: The year of birth is given as both 1897 and 1898.
- Grier, David Alan, "Gertrude Blanch of the Mathematical Tables Project", Annals of the History of Computing, 19.4 (1997), 18-27.
- Grier, David Alan, "The Math Tables Project of the Work Projects Administration: the reluctant start of the computing era", Annals of the History of Computing, 20 (1998), 33-50.
- Grier, David Alan, "When Computers Were Human", 2005.