[1][2] Day is recognized as a pioneer physical anthropologist whose study helped future black researchers and is used to challenge scientific racism about miscegenation.

[5][6] Although Day's work was not well received within contemporary scholarship in the early twentieth century and still remains controversial, her scientific research re-evaluates the accomplishments of African-American women in the white-male-dominated field of physical anthropology and marks the first step in understanding and promoting African-American biological vindication.

She took undergraduate courses with Earnest Hooton, the only physical anthropologist within the academic department at Harvard and became the editor of her research project.

[9] By continuing to collect data from people of mixed black and white ancestry "in her spare time" over the thirteen years,[9] Day successfully published "A Study of Some Negro-White Families in the United States" in 1932.

[3] Her accomplishment brought her the title of the first African-American anthropologist at Harvard to receive a master's degree with first authorship for her research work.

[5] Her research was a unique anthropological study that provided over 400 family photographs and morphological features and possible inheritance patterns and gave a scholarly examination of physiological, biological, and sociological characteristics of race-crossing.

While working on her research in Hooton's lab, Day was able to collect and analyze sociological and physiological information on 346 families, including her own.

[1] These results were published in 1932 by Harvard's Peabody Museum, named "A Study of Some Negro-White Families in the United States".

[9] Day was suffering from recurrent illness, and she died from a stroke due to complications from her chronic heart condition on May 5, 1948, in North Carolina.