In his essays on the taming of the Alaskan wilderness, John McPhee mainly explores two related themes: the importance of ecology and the hazards of development. As he focuses on the singular role of Alaska for the United States, he expands on the theme of the frontier and its importance in American history. McPhee emphasizes the contributions of individuals by profiling those who have taken risks to settle Alaska; in this regard, along with rugged individualism, another theme that is presented (but not fully developed) is masculinity. As the author centers on the period around major federal legislation limiting settlement, he also uses the theme of government relations with private industry.

With large amounts of the state set aside for limited or no development, the 1971 Alaska Native Claims Settlement Act was highly significant for designating the remaining amount available for use. Negotiations between Native Americans and outsiders figured into this agreement, as did the contest between the state and federal governments over land ownership and control. For McPhee, the idea that the American frontier was finally closing is highly significant.

Another essay centers on the state versus federal politics as well as the economic development in the southern part of the state. Here, the topics of centralization and urbanization shows those conflicts through the efforts to decide about where to relocate the state capital.

The author uses three separate essays to develop the often-overlapping themes. In one, he accompanies three men who are surveying the Salmon River in the Brooks (mountain) Range, north of the Arctic Circle. Here, their rugged masculinity is fully evident, along with the risks they face and the importance of their scientific documentation.

The theme of individualism (and its consequences) occupies the third essay, which includes a series of profiles of people in the town of Eagle. Included are the relations between Native Alaskans and the primarily white inhabitants of the town.

The overwhelming significance of the natural environment is fully displayed as McPhee's central concern.