Pioneer 15 of 21 · 1872-1952

Mary Engle Pennington

Contribution. A chemist and bacteriologist, she showed that fresh food keeps far longer at steady low temperatures and turned that finding into standards for milk, poultry, eggs, and refrigerated railroad cars. Her work helped build the modern cold chain in the United States.

Factor coverage

Favorable entries (helped or barrier absent) and adverse entries (barrier or not overcome) by factor. Factor tags are this site's classification.

Biological00 Psychological00 Economic02 Societal34 Cultural01 Social20 Environmental00 Educational12 Technological00

Barriers faced

Factors	Statement
Societal Educational	She completed the coursework at the University of Pennsylvania's Towne Scientific School but in 1892 received a certificate of proficiency instead of a bachelor's degree, because the university did not grant degrees to women.
Societal Economic	Before 1900, women chemists were mostly limited to assistant jobs under men, teaching, or nutrition work.
Economic	With few jobs open to women chemists, she held research fellowships at Penn and Yale and in 1898 cofounded her own laboratory in Philadelphia.
Societal Cultural	Her federal civil service papers were submitted under the name "M. E. Pennington," hiding that she was a woman. When this was discovered, Civil Service officials reportedly tried to withdraw the offer, though her own later account says she was already at work (Stephan, 1996).

What helped

Factors	Statement
Educational Social	Supportive faculty. Penn professors used a rarely invoked university statute for "extraordinary cases" to admit her to graduate study, and she earned a doctorate in chemistry in 1895.
Social Societal	Harvey Wiley. The chief of the Bureau of Chemistry hired her and, according to the Science History Institute, intervened to keep her in the post. In 1907 she became the first chief of the U.S. Department of Agriculture's Food Research Laboratory.
Societal	Local results. Her laboratory's report on Philadelphia's milk supply led to a post at the city health department, and the milk standards she developed were adopted by health boards across the country.
Societal	Wartime demand. During World War I she personally took part in about 500 test journeys of refrigerated railcars over two years, and in 1919 she received the Notable Service Medal from Herbert Hoover.

Not overcome

Factors	Statement
Societal Educational	Penn never awarded her the bachelor's degree she had earned, and her entry into federal service depended on concealing that she was a woman.

Notes

Factors	Statement
none	She worked as a consultant from 1919 to 1952, held five patents (Smithsonian Lemelson Center, Penn Gazette), including a poultry-cooling rack (1912) and a method of treating eggs (1935), received the American Chemical Society's Garvan Medal in 1940, and was inducted into the National Inventors Hall of Fame in 2018.

Pattern summary

Element	In this case
Door-opener	Harvey Wiley
Knowledge source	University of Pennsylvania doctorate
Institutional support	USDA Bureau of Chemistry, Philadelphia health department
Built on recent work	The 1906 Pure Food and Drugs Act, bacteriology
Setback overcome	Denied a bachelor's degree, admitted to doctoral study anyway
Barrier not overcome	Never received her bachelor's degree
Related barriers	Discrimination and exclusion, unequal access to education, infectious disease

Not independently verified. Sources disagree on the year Pennington began leading the Food Research Laboratory (1906 to 1908). Two of her five patents, the 1932 egg-color scale and the egg-freezing method, were not located in patent records. This site follows the stronger or majority source.

Sources

Also relevant: Bell, A., Chetty, R., Jaravel, X., Petkova, N., & Van Reenen, J. (2019). Who becomes an inventor in America? Quarterly Journal of Economics, 134(2), 647-713. All references