The eastern Asian-North American disjunction has drawn the attention of botanists and biogeographers since the mid-19th century and laid the groundwork for early biogeographic theory. Since then, the floristic affinities between eastern Asia and North America have been extensively studied. Physocarpus (Rosaceae) provides an under-studied example of this intercontinental distribution pattern. As currently circumscribed, the genus comprises seven species of temperate deciduous shrubs, with one species in eastern Asia and six in North America. Physocarpus has received relatively little systematic attention to date. A previous phylogenetic study found complex intrageneric relationships, including polyphyletic as well as unresolved taxa. Additionally, the study was not able to resolve the earliest-diverging lineage. However, advances in phylogenomics have the potential to resolve these complex relationships as well as determine the earliest-diverging lineage, which has biogeographic implications. While Physocarpus exhibits an intercontinental disjunction at the genus level, P. intermedius occupies an intracontinental disjunction between eastern and western North America. Its range is further characterized by apparent sympatry with P. opulifolius in the Great Lakes Regions. Although the Flora of North America North of Mexico treats P. intermedius at the species level, this taxon is often treated as P. opulifolius var. intermedius in regional or state floras. Previous work on the geographic distribution of follicle morphology, an important diagnostic trait, supports the recognition of two taxa, but the appropriate rank remains unresolved. The present study has two primary objectives: 1) to infer the earliest-diverging Physocarpus lineage, and 2) to clarify the evolutionary relationship between P. opulifolius and P. intermedius. These are addressed by inferring a coalescent species tree in a Maximum Likelihood framework, as well as phylogenetic inference in a Bayesian framework. The results from this project will inform the systematics and biogeographic history of this disjunct genus.