Though she had a famous affair with American businessman Gilbert Imlay that produced a daughter, Mary Wollstonecraft only married once, and that was to William Godwin, the radical British intellectual. Mary Wollstonecraft Shelley, the author of Frankenstein, was the child of this union. Godwin was the author of a number of books, perhaps most famously the borderline anarchist tract An Inquiry Concerning Political Justice. Wollstonecraft and Godwin moved in the same radical circles in late eighteenth-century England, and began an affair shortly after Wollstonecraft published A Vindication of the Rights of Woman. They married only when Wollstonecraft became pregnant with the future Mary Shelley. Wollstonecraft died shortly after giving birth, but Godwin lived for many years thereafter. He remarried, and later published Caleb Williams, perhaps his most famous literary work. He died in 1836, almost forty years after Wollstonecraft.