This book has evolved over a number of years and, during that time, some of the people who assisted me have died. I would like to acknowledge the late Beekman Pool for sharing his information and research regarding Lincoln Ellsworth. Michael Ross and Dr. David Larson, who lived in Michigan and Washington, DC respectively, both died in November 2016. They were gracious hosts during my visits to them and without their assistance and willingness to let me copy their records, this book would never have been written. Laura Kissel, the polar curator at the Byrd Polar and Climate Research Center (BPCRC), at Ohio State University in Columbus, Ohio, has cheerfully tolerated my requests for information (along with my visits) over many years, and I have to express my thanks, yet again, for her marvelous assistance. Many people have answered my emails and questions, but I would like to highlight the help given me by Kathie Bell, Stephen Carthew, Laraine Daly Jones, Donal Duthie, Ann Kirschner, Steve Kalvar, Jon Larson, Melba Matson, Rob Mulder, Mark Pharaoh, Saskia Raevouri, Kaye Ridge, Dick Smith, Bess Urbahn, Judith K. Thome, Christine Venema, Thomas Vince, and Hal Vogel. Richard Pearl valiantly tried to explain navigation to me in layman’s terms and any errors in my explanations are mine, not his. My literary agent, Andrew Lownie, is always astute in his judgement, and I thank him for introducing me to Claiborne Hancock and the brilliant team at Pegasus Books, who have done a wonderful job with the production of this book. My friend and editor, Rebecca Green, steered me through the many drafts of the manuscript and continually provided valuable insights. As always, my wife, Zoe, and my family provide the support to make this work possible, and I can never thank them sufficiently.