This essay examines Frederick Douglass’s oratory of the 1840s, when religious appeals drove his abolitionist rhetoric. In addressing the lack of critical attention paid to his early oratory and evangelism, the essay argues that these speeches, which he delivered to audiences in the US North and Europe, offer an incisive transatlantic critique of the religious roots of American exceptionalism by attacking American Protestantism and the growing mythology of the nation’s Puritan origins. Douglass’s early speeches undercut the celebration of Puritan ancestry by Daniel Webster, George Bancroft, and others; provide a thick description of US antebellum religious persecution in both the North and South; and deploy missionary rhetoric to call on European Protestant churches to remake their US counterparts. For 1840s Douglass, slavery in the United States was not a result of the country failing to live up to its founding republican principles, an argument he would make in subsequent decades. Rather, the more radical and zealous appraisal of the country he offered at that time was that the country’s founding reliance on slavery and servitude meant that it was, at core, an apostate nation in need of Christian conversion.