Castilleja cusickii Greenm. (Orobanchaceae) is a widespread and highly polymorphic species found growing in wet meadows throughout the northern portion of the Intermountain West and interior Pacific Northwest. Multiple populations throughout its range have been identified and long known to vary both morphologically and ecologically from its typical populations and may constitute distinct taxa. The aim of this study is to revisit the species limits of C. cusickii using a combination of phylogenetic and population genomic approaches. In addition, we have collected an extensive morphological dataset that will be used in combination with molecular data to support our efforts in understanding the diversity of this species complex.