The Stripetail Darter, Etheostoma kennicotti (Putnam), is widely distributed in tributaries of the lower Ohio River, the upper Green River system, the Clarks River system, throughout the Tennessee River system, the Laurel River system, and the upper Cumberland River system. Etheostoma cumberlandicum Jordan and Swain was described in 1883 from a population sampled in the Clear Fork system that drains to the upper Cumberland. A previous morphological analysis led to the placement of E. cumberlandicum into the synonymy of E. kennicotti. Results from molecular phylogenetic and relaxed molecular clock analyses, genetic variation at 25 microsatellite loci, morphological disparity in meristic traits, and variation in pigmentation from specimens sampled throughout the geographic distribution of E. kennicotti (s.l.) indicate E. cumberlandicum is a distinct species and there are multiple undescribed species masquerading as E. kennicotti. We elevate Etheostoma cumberlandicum out of synonymy and propose Moonbow Darter as the common name for the species. The results of the phylogenetic analyses are discussed in the context of the historical biogeography of rivers draining the Eastern Highlands of North America.