Morphological features were examined from more than 5,000 Rubus specimens to prepare the first comprehensive revision of the native and naturalized Rubus of Iowa. Twenty-eight species (one with two varieties) and one interspecific hybrid have been collected in the state. They are described in this revision, which contains keys to subgenera and species designed specifically for field researchers in Iowa and nearby states. Synonymy, distribution, phenology, habitat, associated plants, and taxonomic treatment by past researchers are also discussed. Range-wide county distribution maps are presented for 22 species representing Rubus subgenus Rubus (the blackberries and dewberries), and Iowa county distribution maps have been included for R. idaeus L. var. strigosus (Michx.) Maxim., R. occidentalis L., R. parvifolius L., and R. pubescens Raf. The findings of this study are discussed in the context of the putative reticulate phylogeny among species of Rubus subgenus Rubus, and potential subjects for future molecular and cytological research are proposed.