The grackles (Quiscalus spp.), together with their sister genus Euphagus, compose a clade within the New World blackbirds (Icteridae). We used gene sequences of cytochrome b and NADH dehydrogenase subunit 2 (ND2) to reconstruct relationships within this group. A primary concern was determining the phylogenetic position and genetic distinctiveness of the extinct Slender-billed Grackle (Q. palustris)—a poorly known endemic of the Lerma Basin and the ancient lakes of the Valley of Mexico, last collected and recorded in 1910—and of the Nicaraguan Grackle (Q. nicaraguensis), which is likewise unusual among grackles for its restricted geographic range. Our analysis differs from previous efforts by inclusion of these taxa along with all other recognized grackle species, intraspecific sampling of Greater Antillean (Q. niger), Carib (Q. lugubris), and Great-tailed (Q. mexicanus) Grackles, and inclusion of additional sequence data. The recovered phylogeny reveals Slender-billed Grackle to be most closely related to one of two major haplotype clades of Great-tailed Grackle, the other being sister to Boat-tailed Grackle (Q. major). Nicaraguan Grackle appears sister to Carib Grackle (Q. lugubris). We discuss the implications of these and other relationships in the genus for species limits and biogeography.