While traditional measures of biodiversity are typically based on the species present in an area, phylogeny-based measures are able to capture information about the evolutionary history represented in an assemblage of taxa. Investigations of diversity and endemism using a phylogenetic framework can reveal the distributions of evolutionary lineages and the relative ages of plant assemblages. The South-Central United States (made up of Oklahoma and Texas) is a floristically diverse region that contains ~8,000 vascular plant species. This region is also climatically diverse, with strong abiotic gradients in temperature, precipitation, and elevation. The current understanding of spatial phylogenetics in this region comes from a few continental-scale studies utilizing herbarium data. However, the South-Central US has not yet been included in any regional-scale studies, which could potentially reveal finer-scale patterns not apparent across broader study regions. Additionally, much fewer data have been available from Oklahoma and Texas compared to many other regions of North America; this may have led to incomplete conclusions about the spatial phylogenetics of plants in this region. Recent and ongoing digitization and georeferencing efforts have addressed this data gap by mobilizing a wealth of herbarium records from Oklahoma and Texas. In this study, we aim to use these newly available herbarium data to characterize the spatial patterns of phylogenetic diversity (PD) and phylogenetic endemism (PE) seen in the vascular flora of the South-Central US. This approach has highlighted locations that contain relatively old and young plant assemblages, as well as locations that contain concentrations of old and young lineages with restricted ranges. In addition, we tested for associations between PD, PE, and climatic gradients in precipitation, temperature, and elevation.