Mary Engle Pennington began her professional career as an analytical chemist, earning her Ph.D. under Edgar Fahs Smith at the University of Pennsylvania in 1895. Pennington's post-graduate work led her to the field of bacteriological chemistry and ultimately to refrigeration engineering. Our current confidence in the safe handling, storage, and transportation of foods is due in large part to the work of Mary Engle Pennington.
Mary was born on October 8, 1872 in Nashville, Tennessee to Henry and Sarah Molony Pennington. Soon after, the family moved to Philadelphia in order to be closer to their Quaker relatives. She showed an early interest in chemistry—she had borrowed a book on medicinal chemistry from the public library and found she didn't understand many of the terms. She lived near the University of Pennsylvania campus and so went there for answers. They told her to come back when she was older, which she did. She was admitted to the university in 1890 and completed the degree requirements for a major in chemistry and minors in zoology and botany in 1892. Mary Engle Pennington, however, was awarded a certificate of proficiency rather than a B.S. because the University of Pennsylvania did not grant degrees to women.
After completing her Ph.D. she spent the next two years doing research at the University of Pennsylvania in chemical botany, followed by a year of research with Mendel in physiological chemistry at Yale University. In 1898 she accepted a position as director of the Clinical Laboratory at the Women's Medical College of Pennsylvania. During this time she also worked as a bacteriologist with the Philadelphia Bureau of Health. She not only carried out careful scientific studies on the relationship between handling conditions and bacterial levels in milk and milk products, she also used her work to persuade farmers to agree to new procedures that would help keep milk and milk products safe for the consumer.
In 1905 Pennington began her long association with the U.S. Department of Agriculture (USDA) as a bacteriological chemist. Her exceptional performance there prompted her director (Harvey W. Wiley) at the Bureau of Chemistry to strongly encourage her to apply to become Chief of the Food Research Laboratory that was just being established as a result of the 1906 Pure Food and Drug Act. Because of Mary Engle Pennington's thorough and careful work, she was able to define procedures for every step of the process of taking chickens from the slaughterhouse to the consumer. This was one of her greatest contributions.
In 1919 Pennington accepted a position as director of American Balsa, which manufactured insulation used in refrigeration units. Because she was often consulted about perishable food issues, she started her own consulting firm in 1922, which she ran until 1952 when she retired. During this period Mary Engle Pennington also applied her knowledge to refrigeration, making numerous contributions, especially in the design of commercial and household refrigerators, refrigerated railway cars, and freezers.
Mary Engle Pennington was recognized for her pioneering work: she was elected to the American Society of Refrigerating Engineers, she was awarded the Notable Service Medal from President Hoover in 1919, the Garvan Medal in 1940, and, in 2002, she was inducted into the National Women's Hall of Fame.
After retirement, Dr. Mary Engle Pennington remained active professionally; she was still consulting and was vice president of the American Institute of Refrigeration when she died on December 27, 1952 in New York.