Schlesinger pioneered the new social history and women's history. He was a Progressive Era intellectual who stressed material causes (like economic profit) and downplayed ideology and values as motivations for historical actors. He was highly influential as a director of PhD dissertations at Harvard for three decades. He was well-known for his cyclical view of history (which attracted few followers) and for polling historians to rank presidential greatness, which attracted much attention. Schlesinger was co-editor and contributor of the "History of American Life" series (1928-43), which stressed social, demographic and economic trends, and downplayed politics and individuals. Numerous Schlesinger doctoral students, such as Merle Curti, studied the social analysis of ideas and attitudes. In an essay on "The Significance of Jacksonian Democracy" (in New Viewpoints in American History (1922)) Schlesinger drew attention to the fact that "while democracy was working out its destiny in the forests of the Mississippi Valley, the men left behind in the eastern cities were engaging in a struggle to establish conditions of equality and social well-being adapted to their special circumstances". Himself a historian of the rise of the city in American life, he argued that for a full understanding of the Jacksonian democratic movement: "It is necessary to consider the changed circumstances of life of the common man in the new industrial centers of the East since the opening years of the nineteenth century." This was a challenge to the frontier thesis of his Harvard colleague Frederick Jackson Turner. In Schlesinger's essay, the common man of the Mississippi Valley and the common man of eastern industrialism stood uneasily side by side.
He was born in Xenia, Ohio and graduated from the Ohio State University in 1910. He took his Ph.D. in history at Columbia University. He taught at Ohio State and the State University of Iowa before joining the faculty of Harvard University as a professor of history in 1924. Schlesinger taught at Harvard until 1954. Harvard's Schlesinger Library in women's history is named after him and his wife Elizabeth, a noted feminist. He became an editor of the New England Quarterly in 1928.