Cracker Culture is a provocative study of social life in the Old South that probes the origin of cultural differences between the South and the North throughout American history. Among Scotch-Irish settlers the term "Cracker" initially designated a person who boasted, but in American usage the word has come to designate poor whites. McWhiney uses the term to define culture rather than to signify an economic condition. Although all poor whites were Crackers, not all Crackers were poor whites; both, however, were Southerners.

The author insists that Southerners and Northerners were never alike. American colonists who settled south and west of Pennsylvania during the 17th and 18th centuries were mainly from the "Celtic fringe" of the British Isles. The culture that these people retained in the New World accounts in considerable measure for the difference between them and the Yankees of New England, most of whom originated in the lowlands of the southeastern half of the island of Britain. From their solid base in the southern backcountry, Celts and their "Cracker" descendants swept westward throughout the antebellum period until they had established themselves and their practices across the Old South. Basic among those practices that determined their traditional folkways, values, norms, and attitudes was the herding of livestock on the open range, in contrast to the mixed agriculture that was the norm both in southeastern Britain and in New England. The Celts brought to the Old South leisurely ways that fostered idleness and gaiety. Like their Celtic ancestors, Southerners were characteristically violent; they scorned pacifism; they considered fights and duels honorable and consistently ignored laws designed to control their actions. In addition, family and kinship were much more important in Celtic Britain and the antebellum South than in England and the Northern United States. Fundamental differences between Southerners and Northerners shaped the course of antebellum American history; their conflict in the 1860s was not so much brother against brother as culture against culture.