There are more than 60 currently recognized species of manzanitas (Arctostapylos, Ericaceae), and almost all occur within the political boundaries of the state of California. Most of the species have very small geographic ranges (“narrow endemics”), often making up what looks to be a single population, while a handful of species have larger ranges within California and in some cases, beyond. Due to very small ranges of many manzanita species, genetic diversity within these species may be low. Under the threat of a changing climate, and increasing human-caused disturbances, genetic diversity may be key to the potential for species to adapt, and survive in the long-term. In this study, we use whole genome resequencing data to assess genetic diversity of six narrow endemic manzanita species, from three regions within California, computing measures of genetic diversity. Generating this population genetic information for these six species will serve as a first step in establishing genomically-informed conservation planning, for in situ or ex situ preservation of genetic diversity of threatened manzanita species. Additionally, to put the genetic diversity of these narrow endemics in context, we compare genetic diversity of each narrow endemic species, and each region, to that of a widespread species (Arctostaphylos glauca), whose range encompasses the ranges of all six narrow endemics, and which was sampled across its range in California. With this approach we hope to identify regions within the state where narrow endemics may be most in need of conservation of genetic diversity.