Ancestors of contemporary salamanders were likely able to disperse and migrate into habitats of the Rocky Mountains and surrounding areas by the Eocene. Mesic forests were established in western North America by the mid Eocene and attained their contemporary range distributions by the early Pliocene. The temperate forest valleys and montane environments of these time periods (Paleogene to Neogene) would have provided the physiographic and ecological features supporting analogs of contemporary Ambystoma macrodactylum habitats. The Cascade Range rose during the mid Pliocene and created a rain shadow effect causing the xerification of the Columbia Basin and also altered ranges of temperate mesic ecosystems at higher elevations. The rise of the Cascades causing the xerification of the Columbia Basin is a major biogeographic feature of western North America that divided many species, including A. macrodactylum, into coastal and inland lineages.