Nearly all of the major arguments about the sectional crisis turn on geographic explanations of one sort or another. A number of recent works have taken a comparative approach to slavery within the United States, usually focused on places in the Upper North and Lower South. Though such comparisons of distant areas would seem likely to emphasize difference, historians have found fundamental similarities in social institutions, political cultures, political structures, and economic structures. John Quist's study of nineteenth-century reformers in Michigan and Alabama, for example, emphasized that in both places reform grew in soil rich with evangelical revivals and growing markets. Quist found deep and striking similarities. (Quist, Restless Visionaries)

Historian William Freehling's influential interpretation of the Southern secession crisis proceeds from the view that the Upper South was less dependent on slavery and therefore less essentially Southern. According to Freehling, the closer to the border one traveled from the Deep South the less distinctively southern places became until at the border there the difference was at points invisible. Along the border, "a world between," almost all whites, Freehling wrote, agreed that slavery would fade away. Freehling's "twilight zone" included Virginia, most prominently, which in 1860 had the largest number of enslaved persons of all the states in the South, as well as the largest number of slave holders. (Freehling, Road to Disunion, 19, and The Reintegration of American History, 182)

Other recent scholarship has discovered, by contrast, that in the late antebellum period slavery was expanding into parts of Virginia previously free of the institution. Kenneth Koons and Warren Hofstra's edited volume After the Backcountry: Rural Life in the Great Valley of Virginia, 1800-1900 and Kenneth W. Noe's Southwest Virginia's Railroad: Modernization and the Sectional Crisis reveal the adaptability of slavery in the Shenandoah Valley and in mountainous southwest Virginia. While Koons and Hofstra consider the Valley a "middle ground" and imply that it was a region distinct from both the plantation South and the North, their research and essays indicate the complicity of the Valley in the economy and workings of slavery. Noe finds in Southwest Virginia all the elements of modernization: transportation revolution, shift to the market economy, slavery expansion, dynamic growth of communities, and larger scale agriculture. He contends that the Virginia and Tennessee Railroad "hastened the development of capitalistic, slave-based, cash crop agriculture in Southwest Virginia." Noe's study also indicates the importance of microanalysis of subregions and counties, because the growth of slavery was strongest in certain areas, largely ones connected to the market, and not others. (Noe, Southwest Virginia's Railroad)

Any analysis of the role of slavery in the conflict between the North and the South, and any understanding of its relationship to modernity, then, needs to account for the broad middle of the nation, the "border." The borderland encompassed vast areas of what became the Federal and Confederates sides in the Civil War. Kevin Phillips has argued in a recent book that "Together, the Lower North, Upper South, and Border counted off half of the U.S. states and two-thirds of the population." That may be a bit extravagant, depending on the method of calculation. This sweeping statement is not far wrong if we count, for example, all the Northern counties along the Mason-Dixon Line, Ohio River, and Mississippi River in which a significant number of men voted against Lincoln in 1860 and 1864 or if we count all the slave states south of that line that either did not secede or seceded only in April 1861. (Phillips, The Cousins' Wars)

The historical geographer D. W. Meinig describes the challenge of mapping the sections very well: "we must surely have something more than a simple map of North and South, of a Mason-Dixon Line (even as a shorthand term), of the Union and the Confederacy as two entities, if we are to have any sense at all of what 'secession' meant in this complicated geopolitical structure during its unprecedented crisis." With Meinig's caution ringing in our ears, we might examine the border especially closely. (Meinig, The Making of America)