Mary Engle Pennington was born into a Quaker family in Nashville, Tennessee. Her family's emphasis on education and social responsibility laid the foundation for her future pursuits in science and public service. Her early exposure to scientific ideas fueled her later passion for chemistry and food preservation.

Pennington completed the requirements for a B.S. in Chemistry from the University of Pennsylvania, but was granted a 'certificate of proficiency' instead of a degree, as the university did not formally award degrees to women in chemistry at the time. She persevered and impressed her professors with her exceptional knowledge and dedication.

Undeterred by gender bias, Pennington continued her studies and earned a Ph.D. in Chemistry from the University of Pennsylvania. Her doctoral research focused on organic chemistry, solidifying her expertise in the field and paving the way for her future work in food preservation.

Pennington gained valuable experience in analytical chemistry and bacteriology at the Women's Medical College of Pennsylvania. Here she directed the Clinical Laboratory, demonstrating her leadership skills and further developing her knowledge of microbes and their impact on health, which later proved crucial in her food safety research.

Pennington made a pivotal career move, joining the United States Department of Agriculture (USDA) as Chief of the Food Research Laboratory. In this role, she was responsible for investigating food spoilage and developing methods for safe food handling and preservation, particularly focusing on poultry, eggs, and dairy products.

Pennington played a crucial role in enforcing the newly enacted Pure Food and Drug Act. Her team developed standards for food processing and transportation, ensuring that perishable goods reached consumers safely and preventing the spread of foodborne illnesses. Her work significantly contributed to the development of modern food safety regulations.

Pennington transitioned to private practice as a consulting engineer, specializing in refrigeration and food preservation. She advised food companies on best practices for cold storage, transportation, and distribution, continuing to champion safe and efficient food handling methods across the industry.

Pennington's expertise and contributions to the field were recognized when she became Vice President of the American Institute of Refrigeration. This position further cemented her status as a leading authority on refrigeration technology and its impact on food preservation.

Mary Engle Pennington passed away in New York City at the age of 80. Her pioneering work in food science and refrigeration engineering had a lasting impact on public health and consumer safety. She left behind a remarkable legacy as a trailblazer for women in STEM and a champion for safe and efficient food handling practices.