Platismatia wheeleri was recently described as a species distinct from the highly morphologically variable Platismatia glauca. Previously, P. wheeleri was known only from intermountain western North America in southern British Columbia, Idaho, Montana, Oregon and Washington. After examining collections from the New York Botanical Garden and Arizona State University herbaria we discovered that P. wheeleri was collected in southern California and the Tatra Mountains of Slovakia. The morphology, ecology and biogeography of P. wheeleri are discussed, and the importance and utility of historical collections is highlighted. This article is intended to alert researchers to the potential presence of P. wheeleri in different regions of the world so we can better understand its historical and current distribution and abundance.