Between 1973 and 2002, Mary Dawson and team spent 11 field seasons searching for vertebrate fossils on Ellesmere, Axel Heiberg, Devon, Ellef Ringnes, Bylot, and Banks Islands in Canada's Arctic Archipelago. Their pioneering efforts resulted in one of the greatest discoveries in vertebrate paleontology of the twentieth century—the first, and best, record of Paleogene terrestrial vertebrates from within the Arctic Circle. Here we provide a history of the field research and discoveries by Dawson and collaborators in the Canadian High Arctic. Discovery of Eocene vertebrate faunas in the Eureka Sound Group on Ellesmere and Axel Heiberg Islands supports the former existence of a high-latitude land connection between Europe and North America, provides insight into the origin of certain mammalian taxa such as microparamyine rodents, and yields evidence for a warm, temperate High Arctic climate at that time. Moving up in the section, Dawson's discoveries in Haughton Astrobleme on Devon Island include the only known High Arctic Miocene terrestrial vertebrate fauna and sparked many other studies ranging from dating the impact crater to palynological and paleoclimatic studies. Dawson's legacies include a large body of literature on High Arctic paleontology and geology by herself, her colleagues, and those she inspired and mentored. Just as important, Dawson's pioneer discoveries provide the impetus and inspiration for further exploration of the High Arctic.