We used PCA of morphological characters to confirm the presence of an undescribed Calamagrostis species in Washington and Oregon that has historically been attributed to Calamagrostis vaseyi. We propose to name this grass Calamagrostis tacomensis. It is most similar to C. foliosa although it has often been confused with C. purpurascens and C. sesquiflora all of which have similar lemma awn characteristics (i.e., the awn relatively long, exserted, and bent). Calamagrostis tacomensis has been collected at high elevations (490–2170 m) in the Washington Cascades, the Olympic Peninsula and the Steens Mountains of Oregon. The name C. vaseyi has been misapplied to our new species. The description of C. vaseyi is similar to C. rubescens. We have studied the specimen that has been attributed to be the type of C. vaseyi and it is C. purpurascens. We lectotypify C. vaseyi.