The taxonomy of Pantherophis has been a complicated area of research. The genus was named by the Austrian zoologist Leopold Fitzinger in 1843, with the type species being Pantherophis guttatus. Shortly after, the genus was then considered to be a junior synonym of the otherwise Old World genus Elaphe. However the morphology of the hemipenes, the dentition, and the squamatization found the New World species to be closer to the genus Pituophis (gopher snakes, pine snakes, and bullsnakes). Subsequent molecular studies have found support of the sister grouping between Pituophis and the North American Elaphe species, which resulted in the resurrection of the genus Pantherophis.Utiger, U.; Helfenberger, N.; Schätti, B.; Schmidt, C.; Ruf, M.; Ziswiler, V. (2002). "Molecular Systematics and Phylogeny of Old and New World Ratsnakes ..." Russian Journal of Herpetology 9 (2): 105-124. These two genera, along with several other North American endemic taxa like Lampropeltis belong to the tribe Lampropeltini.
