  In 1925, at the age of 66, Cooper earned a Ph.D. at the Sorbonne in Paris, France becoming the fourth Black American woman to earn a Ph.D. The first three black women to earn the Ph.D. in the U.S. include Sadie T.M. Alexander (University of Pennsylvania), Georgianna Rosa Simpson (University of Chicago), and Eva B. Dykes (Radcliff College) and each did so in 1921. Cooper recalls the Herculean effort required to complete her exams and thesis for the doctorate in The Third Step. She took courses at La Guilde Internationale, Paris in French Literature, History, and Phonetics during the summer months in 1911, 1912, and 1913. After starting her doctoral studies at Columbia University in New York in the summer of 1914, Cooper would then take guardianship of five children (her great-nieces and nephews) and in 1916 she purchased a five-bedroom home in which to raise them. By 1917 she earned thirty-two credits and was certified in French, Latin, and Greek at Columbia. However, Cooper could not meet the one-year residential requirements as she was still working at M Street High School in Washington, D.C. She later decided to transfer her credits from Columbia to the University of Paris in France. In December of 1923 Cooper came down with influenza and asked for a sick leave from her teaching obligations. By February 1924 she selected her thesis topic, but then learned that she had only sixty days to return to her teaching post or be “dropped” from her position at M Street High School. Cooper returned to her teaching position on the sixtieth day and continued to do research and writing on the thesis at the Library of Congress on evenings and weekends. She defended her thesis on March 23, 1925 and received her diplôme de Docteur ès lettres de la Faculté de Paris on December 29, 1925 in a ceremony supported by the Alpha Kappa Alpha sorority at Howard University.