During an age of celebrated polar adventurers, ambitious young geologist Ernest deKoven Letting well traveled to the Arctic as chief scientist for the 1901 Baldwin-Ziegler Expedition. He experienced the dangers of living and traveling in an extreme environment as he learned to operate delicate scientific instruments under harsh conditions. Then, with fellow explorer and friend Ejnar Mikkelsen, Leffingwell co-organized the 1906 Anglo-American Polar Expedition. Despite the perils and challenges of navigating pack ice, they determined the edge of the continental shelf-the first solid evidence that there was no land north of Alaska. Leffingwell stayed behind, and with assistance from his Inupiaq neighbors, the dedicated, driven risk-taker explored, surveyed, and documented geography along Alaska's north coast and geology in what is now the Arctic National Wildlife Refuge (ANWR). On the North Slope of the Brooks Range, he pioneered research in ground ice (permafrost), recorded observations of wildlife, and collected specimens for the Smithsonian and other institutions. Scientists and scholars still admire and use his groundbreaking work.