Orconectes macrus (Neosho Midget Crayfish) and O. nana (Midget Crayfish) are a proposed sister-species pair with a small range on the western edge of the Ozark Highlands Physiographic province. Originally proposed as subspecies, O. macrus was elevated to full species status without explicit reason. This study utilized a single-locus mtDNA region (cytochrome oxidase I) to test: (1) monophyly of the species pair, (2) monophyly of the proposed species, and (3) examine if full species status is warranted for O. macrus. Phylogenetic reconstructions indicate that the two taxa indeed comprise a species pair and that each species is well supported as monophyletic. Additionally, there is significant phylogeographic structuring within each recognized species at fine spatial scales.