Actually, the Republican party was founded as an abolitionist movement. Central to it's original plank was the abolition of slavery. Before the civil war...
Slavery in the colonies helped produce a boom in the 18th century economy that provided the launching pad for the industrial revolution in Europe. From the start, colonial slavery and capitalism were linked. While it is not correct to say that slavery created capitalism, it is correct to say that slavery provided one of the chief sources for the initial accumulations of wealth that helped to propel capitalism forward in Europe and North America.
Throughout the 1700s, what was called the “triangular trade” developed between the colonies, European mother countries (in this case England), and the West African coast. Ships carrying slave-produced sugar, indigo, tobacco, or rice departed the colonies to England, where they were exchanged for manufactured goods. Ships carrying manufactured goods, fabrics, guns, and other finished products traveled from England to Africa where their cargoes were traded for slaves. Then the ships carrying slaves sailed to the colonies, where they were sold for a cargo of colonial produce to be taken back to England—and to start the circuit all over again. By 1750, hardly any trading town in the colonies or in England stood outside the triangular trade. The profits that were squeezed out of the triangular trade formed that capital that led to the boom that made Britain the first major capitalist power.
The clearest example of the connection between plantation slavery and the rise of industrial capitalism was the connection between the cotton South, Britain and, to a lesser extent, the Northern industrial states. Here we can see the direct link between slavery in the U.S. and the development of the most advanced capitalist production methods in the world. Cotton textiles accounted for 75 percent of British industrial employment in 1840, and, at its height, three-fourths of that cotton came from the slave plantations of the Deep South. And Northern ships and ports transported the cotton.
To meet the boom in the 1840s and 1850s, the planters became even more vicious. On the one hand, they tried to expand slavery into the West and Central America. The fight over the extension of slavery into the territories eventually precipitated the Civil War in 1861. On the other hand, they drove slaves harder—selling more cotton to buy more slaves just to keep up. On the eve of the Civil War, the South was petitioning to lift the ban on the importation of slaves that had existed officially since 1808.
Marx clearly understood the connection between plantation slavery in the cotton South and the development of capitalism in England. He wrote in Capital:
While the cotton industry introduced child-slavery into England, in the United States it gave the impulse for the transformation of the more or less patriarchal slavery into a system of commercial exploitation. In fact, the veiled slavery of the wage-laborers in Europe needed the unqualified slavery of the New World as its pedestal.ÖCapital comes dripping from head to toe, from every pore, with blood and dirt.
International Socialist Review