The Melanoplus scudderi species group, when erected by Blatchley, contained six species. The revision of the group presented here describes 21 new species and establishes the Melanoplus carnegiei group, all of which are associated with grasslands in the Southeast. Analysis of DNA barcoding data, suggest that the technique does not adequately delineate species based on the morphological concepts presented here, but did produce three broad mitochondrial DNA clades that correspond to the Apalachicola and Mississippi River discontinuity phylogeographic pattern displayed by several other organisms in the Southeastern United States. This pattern is attributed to vicariant events resulting from Pleistocene glaciation. A hypothetical evolutionary history of the Scudderi and Carnegiei groups is presented. Natural grasslands historically covered a significant portion of the southeastern United States. These grasslands contribute significantly to the biodiversity of the region with many endemic or rare species inhabiting them. Grasshoppers are important components of temperate grassland ecosystems, but no comprehensive review of the grasshopper fauna of southeastern grasslands had previously been conducted. Here a review of the regional fauna was conducted. In total, 211 grasshopper species have been documented in the Southeast, with 111 species (53%) being endemic to natural grasslands. Of particular note, 74 species (34% of the regional fauna) are endemic to the longleaf pine ecosystem. Many of the non-endemic grasshopper species inhabiting grasslands in the region are disjunct from larger populations west of the Mississippi River, presenting interesting biogeographic distributions. Additionally, a cluster analysis of grasshopper community composition from several types of grasslands in the region supports the faunal distinctiveness of the different types grasslands in the region.