In the tradition of James Fenimore Cooper’s Leatherstocking romances, The Big Sky is distinguished among other fine historical novels for its realism and sharp insight into the psychology of the American Western pioneer. Like Cooper’s adventure fiction, A. B. Guthrie’s book explores the clash between two cultures: that of the retreating Indian tribes and that of the advancing Yankee frontiersmen. As the frontier expands westward, the Indians are forced to surrender their lands, their freedom, and their spiritual heritage. In the unequal struggle, the white pioneer, too, loses a portion of his heritage: a sense of idealism.

The “big sky” of Guthrie’s title is the vast open land of the frontier, once teeming with wildlife, but slowly—even within the chronology of the novel, 1830 to 1843—changing, with the slaughter of buffalo, beaver, and other creatures of the forest and plains. In his descriptions of the land, its vegetation, and its animals, as well as of the rough frontiersmen, Guthrie has the eye of a naturalist; the smallest detail does not escape his attention. From The Big Sky, one learns how deer, elk, and mountain goats survive in the wilderness, how rivermen operate a keelboat, how fur hunters kill and strip game, and how mountain men endure the bitter Northern winters. Unlike many other adventure stories treating the West, Guthrie’s novel is without sentimentality. For the hunters, traders, and marginal farmers of the outlying territories, life is hard and often brutal. In his realism, Guthrie does not gloss over the harsh truths of the time. Trapped in a winter storm without food, Beauchamp becomes a cannibal and devours his dead companion, Zenon. Boone Caudill murders his best friend, Jim Deakins, whom he wrongly suspects of fathering his son. Guthrie’s treatment of the Indians is similarly unsentimental. The squaws who mate with the white hunters are described, for the most part, as dirty, complaisant whores; whole tribes, like the Piegans, are wiped out by smallpox; others are reduced to the condition of drunkards. Poordevil, the Blackfoot who accompanies Boone, Jim, Dick Summers, and the other trappers, is a hopeless alcoholic. Thus, to Guthrie, the clash between the two cultures brutalizes both the white people and the native Indians.

In his analysis of the characters’ motivations, the author is also a tough-minded realist. His protagonist, Boone, is a violent, headstrong, mostly insensitive man whose redeeming virtue is his loyalty. Throughout most of his adventures, he trusts, with good reason, his longtime friend Jim. Yet, at the last, he kills Jim when he fears, mistakenly, that his friend has betrayed him. In a similar vengeful action, he abandons his beloved Indian wife, Teal Eye, when he suspects her of adultery. From these impulsive actions he brings about the ruin of his dreams. Guthrie once wrote that the theme of The Big Sky (paraphrasing Oscar Wilde) is that each man destroys the thing he loves best. Nevertheless, Boone’s destructive impulse results as much from his early experiences as from his conscious will. Abused by his father, robbed by the clever rascal Jonathan Bedwell, cheated by the law, Boone has come to regard men warily, as objects of his revenge. His passions, too elemental to be curbed by reason, run their course, as in Greek tragedy. In a larger sense, however, his personal defeat is insignificant compared to the greater tragedy of the dwindling American frontier. Although Boone and his fellow frontiersmen love the land, they are at least partly responsible for ravaging it. By 1843, the year when the novel ends, much of the frontier still remained, but the pattern for its destruction had already been established. The “big sky,” like the mountain men’s idealistic ambitions, would henceforth be diminished.