Miller joined the Army in 1943 and was stationed in Los Alamos. Based on her credentials and talent, Los Alamos administrators placed her in charge of one of the chemistry laboratories.
While she was offered a higher military rank to match her leadership position, Miller refused promotion from her private rank as a matter of principle. Miller was a member of the Women's Army Corps until 1945.
In May 1945, she was one of the sixty-seven WACs at Los Alamos and helped make up the forty percent of whom worked in the facility's scientific areas. According to Their Day in the Sun: Women of the Manhattan Project, this was a "higher percentage than the figure for all Los Alamos staff" (p. 149).
Miller earned her bachelor's degree from Syracuse University in 1927. She pursued graduate degrees at Columbia University and earned her master's degree and Ph.D. in 1929 and 1934, respectively.
In between her master's and Ph.D. studies at Columbia, she also taught at St. Mary's Junior College in North Carolina from 1931 to 1932. After graduating from Columbia, she became a chemist at Rockefeller University.
When World War II began, Miller was working as a research associate at Washington University in St. Louis's School of Medicine.
Following World War II, Miller became a research fellow at the American Cyanamid Company in Stamford, Connecticut. She worked at the company as a chemist until she retired in 1969.
For more information about Mary Lucy Miller and women in the Manhattan Project, please see the following reference: