Vernon Louis Parrington, whose Main Currents in American Thought has been the most influential Jeffersonian statement of American intellectual history in the twentieth century, must be numbered among the Progressive school of historians. Unlike Charles Beard and Frederick Jackson Turner, however, his contribution came late and rested upon a single uncompleted work. Few historians have been so obscure as Parrington, so suddenly famous, so latterly unread. Like the agrarian revolts he celebrated, he came from the American hinterland, touched the centers of power, and then retreated without explanation, leaving only the text of his magnum opus as graceful testimony of the disturbance.

Parrington was born in Aurora, Illinois, in 1871. His grandfather, John Parrington, had immigrated from Yorkshire in the 1820s, a fugitive from English industrial change and unrest, an enthusiast for the radicalism of Tom Paine. His father, John William Parrington, had been born in Maine and had...