The North American Civil War in Die Presse by marx argues, among other things:

The cultivation of the southern export articles, cotton, tobacco, sugar , etc., carried on by slaves, is only remunerative as long as it is conducted with large gangs of slaves, on a mass scale and on wide expanses of a naturally fertile soil, which requires only simple labour. Intensive cultivation, which depends less on fertility of the soil than on investment of capital, intelligence and energy of labour, is contrary to the nature of slavery. Hence the rapid transformation of states like Maryland and Virginia, which formerly employed slaves on the production of export articles, into states which raise slaves to export them into the deep South. Even in South Carolina, where the slaves form four-sevenths of the population, the cultivation of cotton has been almost completely stationary for years due to the exhaustion of the soil. Indeed, by force of circumstances South Carolina has already been transformed in part into a slave-raising state, since it already sells slaves to the sum of four million dollars yearly to the states of the extreme South and South-west. As soon as this point is reached, the acquisition of new Territories becomes necessary, so that one section of the slaveholders with their slaves may occupy new fertile lands and that a new market for slave-raising, therefore for the sale of slaves, may be created for the remaining section. It is, for example, indubitable that without the acquisition of Louisiana, Missouri and Arkansas by the United States, slavery in Virginia and Maryland would have been wiped out long ago. In the Secessionist Congress at Montgomery, Senator Toombs, one of the spokesmen of the South, strikingly formulated the economic law that commands the constant expansion of the territory of slavery. "In fifteen years," said he, "without a great increase in slave territory, either the slaves must be permitted to flee from the whites, or the whites must flee from the slaves."

Do historians agree with this analysis?