Helianthus verticillatus Small was first collected in western Tennessee by S.M. Bain in 1892. J.K. Small described it as a new species in 1898. The species was not seen again in the century following the original collection. It has had varied treatments over the years, as a species or as a hybrid. Between 1994 and 1997, several subpopulations were found and studied in northwestern Georgia and northeastern Alabama. In 1998 it was rediscovered in western Tennessee, near the original site, but apparently not at the same site. Analyses of the morphology of the H. verticillatus, along with a determination of the chromosome number, have permitted an updated morphological description and the conclusion that this taxon is not a hybrid, but a good diploid species of sunflower.