Northern reactions to the antebellum South can only be fully understood in the context of northern concerns for the future of the American republican experiment, which was at base the search for an American national identity. Central to antebellum concerns in this regard was the issue of freedom in a nation which yet retained slave labour. In the nineteenth century, the belief in freedom was, in Fred Somkin's words, “the res Americana, the matter of America.” In the decades preceding the Civil War, however, North and South came to hold very different ideas of what freedom meant, and what it entailed. In time, northern concerns over slavery and the society that relied upon it found political expression in what Eric Foner termed the “Republican critique of the South.” This critique was not focussed on slavery alone but on the South as a whole; its society, culture, industry, and intellectual achievements. It was both an attack on the South and an affirmation of northern superiority. Ultimately, it was a sectional message with national ambitions. The “matter of America” became the matter of the North. How this happened, however, has never been adequately explained.

This essay seeks to shed some light on the background to the “Republican critique” by looking in particular at the career of Horace Mann of Massachusetts, specifically at his brief period in Congress (1848–52) during which he adopted an increasingly confrontational stand toward slavery and the South.