This is the story of the opening up of North America's last frontier, of what is being achieved today under the impact of war and what can be achieved tomorrow. It is the story of a frontier which is both American and Canadian, since it cannot be geographically and economically separated, embracing an area extending from the Mackenzie River to the Bering Strait, and taking in parts of the Northwest Territories, northern Alberta and British Columbia, the Yukon and Alaska. It is potentially as important to North America in the twentieth century as the opening up and development of the West in the last century.