Historians have long argued over the relationship of slavery to the world beyond slavery. Nineteenth-century slavery depended on shipping, exchange, communication, banking, and state formation associated with the cutting edge of historical change. On the other hand, forced labor clashed with ideals of individual autonomy, fluid labor markets, personal freedom, mechanization, and democracy considered synonymous with that change.

Both defenders and opponents of slavery wrestled with these polarities. Apologists for slavery sometimes claimed the institution as a crucial part of Western progress and other times portrayed slavery as an essential counterweight to destructive forces of modernity. Opponents of slavery sometimes portrayed the institution as the logical conclusion of rapacious economic development and sometimes as an impediment to the spread of benign institutions of free labor and free institutions. The debate held particular force in the United States, where one of the most advanced industrial economies in the world lived alongside the richest and most powerful slave society in the hemisphere.

The primary difference slavery made, of course, was in the lives of African Americans: hundreds of thousands of individuals tortured and families torn apart, desperate individual and collective acts of perseverance and resistance, and in the face of law, power, and authority, the creation of spiritual communities. That difference, the subject of an immense and rich historiography, is not the focus of this article, which focuses on the relationship between slavery and the forms of white society.

Some historians focus on the intrinsic opposition between slavery and the institutions of modernity, but recently scholars have tended to focus on the symbiosis among slavery, capitalism, and the modern state. Robin Blackburn has put the issue clearly, arguing that slavery in the Americas "was associated with several of those processes which have been held to define modernity: the growth of instrumental rationality, the rise of national sentiment and the nation-state, racialized perceptions of identity, the spread of market relations and wage labour, the development of administrative bureaucracies and modern tax systems, the growing sophistication of commerce and communication, the birth of consumer societies, the publication of newspapers and the beginnings of press advertising, 'action at a distance' and an individualist sensibility." (Blackburn, The Making of the New World Slavery, 4)

Studies such as Blackburn's, ranging across centuries, vast oceans, and broad continents while synthesizing detailed secondary works, are of course essential to our understanding. Another approach to understanding the complex interplay between slavery and the forms of emergent modernity might be found closer to the ground, in a detailed comparison of two places which shared virtually everything except slavery. That is our approach in this article, which explores a paradox that lies at the heart of the study of slavery in the United States in the mid-nineteenth century. The difference slavery made is widely recognized to be profound and yet study after study has shown that slavery did little to create differences between North and South in voting patterns, wealth distributions, occupation levels, and other measurable indices. How should we understand that paradox?