Gamochaeta (Compositae) is a genus of 50–80 herbaceous species with a center of diversity in South America and with several common, generally weedy species in the eastern United States. Historically, some authors recognized as few as one species in the eastern United States while others have recognized as many as eight. These increased numbers are a product of both naturalization of nonnative species and recognition of new taxa. A study was undertaken with DNA markers to assess whether the putative species of this region exhibit genetic differences and to determine if DNA markers may be useful tools for identification. One nuclear and one plastid region of DNA were sequenced, and unique nuclear markers were found for all eight recognized species and unique plastid markers were found for five of the eight species. These results support the species hypotheses for entities in this region. Unlike other genera of the Compositae (e.g., Solidago) that possess little genetic differentiation in commonly used barcoding regions of DNA, the species of Gamochaeta in the eastern United States can be identified using a single nuclear marker, and several may be identified with a single plastid marker. Given that species of Gamochaeta are naturalizing in many places on Earth, these data will provide an important resource for identification.