When early reviewers of Darwin's On the origin of species chided him for neglecting to mention predecessors to his theory of evolution, he added an “historical sketch” in later editions. Among the predecessors he cited was a French émigré to America named Constantine Samuel Rafinesque, who in the mid-1830s had written about the emergence of new species at a time when most naturalists (including Darwin initially) accepted the biblical story of creation and assumed the immutability of species. Rafinesque discovered and named thousands of new plants and animals in his American travels and flooded the taxonomic literature with reports, which seemed incomplete, confusing, and excessive to other naturalists. He alienated many who later dismissed his findings and excluded them from the biological literature. Soon after Rafinesque's death in 1840, Asa Gray, the young American botanist, wrote a damning critique of his work and suggested it be ignored. How Darwin learned of Rafinesque and his views on species is the focus of this essay, which also mentions briefly the two other American naturalists cited by Darwin in his sketch. Gray seems the likely informant through his correspondence with Darwin or his close associates.