A population genetics study was conducted on three plant taxa in the genus Physaria that are found on the Kaibab Plateau (Arizona, USA). Physaria kingii subsp. kaibabensis is endemic to the Kaibab Plateau, and is of conservation concern because of its rarity, limited range, and potential threats to its long-term persistence. Additionally, the taxon is a candidate for federal protection under the Endangered Species Act. It was not clear how genetically isolated P. k. subsp. kaibabensis was from Physaria kingii subsp. latifolia, which is a widespread subspecies found throughout the southwestern USA, including on the Kaibab Plateau. Additionally, other authors have suggested that P. k. subsp. kaibabensis may hybridize with Physaria arizonica, a different species that is also widespread and found on and off the Kaibab Plateau. We conducted a population genetics study of all three groups to better determine the conservation status of P. k. subsp. kaibabensis. Genetic data are in the form of nuclear DNA microsatellites for 13 loci (all apparently diploid). Additionally, we have included location information for the collection sites. We collected tissue samples from on and off the Kaibab Plateau. The overall findings are shared in a manuscript being submitted for peer-review.