This article explores the development of a “prophetic” poetic mode in the writings of self-proclaimed Jewish poet Adah Isaacs Menken (1835–1868). Although Menken laid claim to a Jewish identity, it now appears all but certain that she was neither born Jewish nor underwent any sort of formal conversion. Nevertheless, her self-positioning is highly instructive, since it reveals how the symbolic meanings associated with Jewishness in nineteenth-century America could be pressed into the service of an experimental and culturally subversive literary project. I argue that Menken’s “prophetic” or “Israelite” texts of the 1860s drew upon and mediated between two broader cultural trends: the resurgent apocalyptic strain in antebellum American Protestantism and the post-denominational naturalism and experimental poetics of Walt Whitman. Her idiosyncratic engagements with these trends enabled her to break free of the codes of literary sentimentalism that shaped her early poems and delimited her cultural role as a woman in American culture.