He was born in Brooklyn, New York on February 15, 1899, to Jewish immigrant parents Julius and Sarah (née Kasindorf) Josephson.
His wife, librarian of the American Academy of Arts and Letters and an author in her own right, worked closely with her husband on various projects throughout their careers.
Josephson was also a regular contributor to The New Republic, The Nation, The New Yorker, and the Saturday Evening Post.
Beard and the Depression, and with only one major exception, Stendhal: or the Pursuit of Happiness (1946), Josephson changed his focus of interest from literature to economic history when he published The Robber Barons in 1934.
This was followed by more full-length works in which Josephson served as a spokesman for intellectuals of his generation who were dissatisfied with the social and political status quo.