The breve species group includes closely related Bembidion Latreille ground beetles commonly found at high elevation in the mountains of western North America. For several decades, the group has been considered to consist of two species. Here, we present evidence from morphological, molecular and geographic data that the group contains nine species: Bembidion ampliatum, B. breve, B. geopearlis, B. laxatum, B. lividulum, B. oromaia, B. saturatum, B. testatum and B. vulcanix. We describe three species (B. geopearlis, B. oromaia and B. vulcanix) as new and resurrect four previously synonymized names (B. ampliatum, B. lividulum, B. saturatum and B. testatum). Species diversity is highest throughout the Cascades in Oregon and Washington, and Sierra Nevada of California, where up to seven species can occur in sympatry. We resolved challenging nomenclatural issues through analysis of sequences obtained from century-old type specimens by using a novel application of rDNA copy number analysis – an approach that may prove useful for other historical specimens.