Some southern apologists for slavery argued, among other things, that free labor in the North amounted to ‘wage slavery’ and that northern factory workers and hired hands were actually worse off than African-American slaves in the South. In this respect these defenders of slavery, notably George Fitzhugh, "seemed to speak in Marxist accents," as Dennis Wrong notes. But other defenders of slavery evinced a very un-Marxist contempt for manual labor in general. James McPherson draws attention to some revealing quotations (italics in original):
"The great evil of Northern free society," insisted a South Carolina journal, "is that it is burdened with a servile class of mechanics and laborers, unfit for self-government, yet clothed with the attributes and powers of citizens." A Georgia newspaper was even more emphatic in its distaste. "Free Society! We sicken at the name. What is it but a conglomeration of greasy mechanics, filthy operatives, small-fisted farmers, and moon-struck theorists?... The prevailing class one meets with [in the North] is that of mechanics struggling to be genteel, and small farmers who do their own drudgery, and yet are hardly fit for association with a Southern gentleman’s body servant." Abraham Lincoln and the new Republican Party of the time responded with a vigorous defense of free labor. However, as Eric Foner observes, Lincoln saw wage labor as a stepping stone that young men would take en route to becoming independent artisans, shopkeepers or entrepreneurs, rather than as a permanent feature of the American economy, though it was already becoming that in many cities in the mid-19th century, a process that would intensify after the Civil War. The notion that work has an inherent dignity and overarching societal purpose–that, as William Seward said, "the free-labor system…brings into the highest possible activity all the physical, moral and social energies of the whole State" – fit most comfortably with the world of Lincoln’s youth and young adulthood. It was more difficult to reconcile that notion with the working conditions and standardized production methods of mass manufacturing.
What of the dignity-of-labor ideal in ‘post-industrial’ societies? In an economy dominated by services in which a relatively small proportion of the population is engaged in direct production of tangible goods, it is still possible to speak of people taking pride in their work, irrespective of its nature, even irrespective of whether it is remunerated. But the ideal of the dignity of labor has slipped out of public discussion. Competitiveness is the lodestar of contemporary political-economic discussion in the U.S., along with debt and deficits. Attention is paid to the high unemployment rate, but as much for electoral considerations as any others. An attack by a right-wing governor on the right to collective bargaining sent thousands of people into the streets in Wisconsin, but that action was framed (quite understandably) as a defense of rights rather than primarily as a defense of the dignity of labor. And all sides use the discourse of rights. Thus laws restricting the prerogatives of unions are called right-to-work laws, and states where they are in force are known as right-to-work states -- as if the primary motive of such laws were to guarantee rights rather than to weaken unions. Ultimately, the meaning of 'rights' is determined by political struggles. As Samuel Bowles and Herbert Gintis put it: "Elements of a political lexicon – such as the discourse of rights – do not…have essential meanings…. Making history is often a matter of making language. But discourses are more often borrowed or stolen than created de novo. Faced with a restricted political vocabulary, political actors appropriate and transform tools that even hostile forces have labored to develop." 
Once slavery ceased to exist in the U.S., free labor had no polar antithesis to give it luster by comparison, and it tended to become, at best, just a fact rather than something to be widely celebrated. Critics of wage labor as exploitation could pursue their critique, secure in the knowledge that the surface similarities of their position to that of a George Fitzhugh probably would no longer be flung in their faces. This liberation, so to speak, of the critics of industrial capitalism arguably counts as one of the Civil War’s less-noticed consequences.
P.s. I had intended this post to have a broader, less U.S.-centric focus, but that proved beyond my capacities at the moment.
1. Dennis H. Wrong, The Problem of Order (1994), p.32.
2. James M. McPherson, Battle Cry of Freedom (1988), p.197.
3. Eric Foner, The Fiery Trial (2010), pp.115-16.
4. Quoted in McPherson, p.198.
5. Samuel Bowles and Herbert Gintis, Democracy and Capitalism (1986), pp.161-62.
See also two books by Jonathan A. Glickstein: American Exceptionalism, American Anxiety: Wages, Competition, and Degraded Labor in the Antebellum United States (2002) and Concepts of Free Labor in Antebellum America (1991).