In the 1940s, Flexner began researching the 19th-century labor struggles of American women but found that few historians had touched on the subject. She was by that time already planning to write a history of the American woman suffrage movement and gradually became convinced that a comprehensive treatment must deal with the experiences of working class women and politically active women of color. Flexner worked on the manuscript that was to become "Century of Struggle" through most of the 1950s. Her original publisher, Harper, refused to publish it unless she removed the parts about women of color. Fortunately, when she showed the completed book to the historian Arthur Schlesinger, he recognized its value and urged her to offer it to Harvard University Press, which readily accepted it for publication. It was published in 1959.