US history has been profoundly shaped by the existence of regions and regional consciousness, though the terms “sections” and “sectionalism” were more commonly used until the late nineteenth century. In its formative moments - the Continental Congress and the Constitutional Convention - the new republic was already divided along sectional lines that in turn marked out different economic, social, political, and security interests. Indeed, two of the defining “facts” about the United States of America - the existence of slavery and the presence of (so-called) “free land” in the West - made sectional politics inevitable. From them emerged the North-South and the East-West polarities in American politics and culture. Moreover, the three-sided contest among the Northeast, the South, and the West was one of the preconditions for the American Civil War (1861-5), with the South squared off against the North for control of the trans-Mississippi West. Without slavery there would have been no war, but had the peculiar institution been scattered evenly across the continent, it is hard to imagine that there could have been a sectional crisis.