text from Karl Marx - The American Civil War, as found at libcom.org: In the Northern states, where Negro slavery is in practice unworkable, the white working class would gradually be forced down to the level of helotry. This would fully accord with the loudly proclaimed principle that only certain races are capable of freedom, and as the actual labour is the lot of the Negro in the South, so in the North it is the lot of the German and the Irishman, or their direct descendants. The present struggle between the South and North is, therefore, nothing but a struggle between two social systems, the system of slavery and the system of free labour. The struggle has broken out because the two systems can no longer live peacefully side by side on the North American continent. It can only be ended by the victory of one system or the other. If the border states, the disputed areas in which the two systems have hitherto contended for domination, are a thorn in the flesh of the South, there can, on the other hand, be no mistake that, in the course of the war up to now, they have constituted the chief weakness of the North.

text from Karl Marx - The American Civil War, as found at libcom.org: In the Northern states, where Negro slavery is in practice unworkable, the white working class would gradually be forced down to the level of helotry. This would fully accord with the loudly proclaimed principle that only certain races are capable of freedom, and as the actual labour is the lot of the Negro in the South, so in the North it is the lot of the German and the Irishman, or their direct descendants. The present struggle between the South and North is, therefore, nothing but a struggle between two social systems, the system of slavery and the system of free labour. The struggle has broken out because the two systems can no longer live peacefully side by side on the North American continent. It can only be ended by the victory of one system or the other. If the border states, the disputed areas in which the two systems have hitherto contended for domination, are a thorn in the flesh of the South, there can, on the other hand, be no mistake that, in the course of the war up to now, they have constituted the chief weakness of the North.