Directly following her time at Yale, Cromwell became a professor of English Language and Literature at University of the District of Columbia, later becoming Head of the literature department. She taught there until her retirement in 1944. Throughout her academic career, Cromwell worked to advance the cause of civil rights and racial and gender equality. Upon her retirement, Cromwell began what was to be her major scholarly work, The Life of Lucretia Mott (Harvard University Press, 1958). Cromwell edited Readings from Negro Authors,"Readings from Negro authors : for schools and colleges, with a bibliography of Negro literature". WorldCat. an early anthology of African-American literary contributions.
