In 1860, 5 of the 10 wealthiest states in the US are slave states; 6 of the top 10 in per capita wealth; calculated just by white population, 8 of 10. The single wealthiest county per capita was Adams County, Mississippi. (Photos of some of the plantation houses.) As a separate nation in 1860, the South by itself would have been the world's 4th wealthiest, ahead of everyone in Europe but England. Italy did not enjoy an equivalent level of per capita wealth until after WWII; the South's per capita growth rate was 1.7%, 1840-60, 1/3 higher than the North's and among the greatest in history.

from Walter Johnson, "King Cotton's Long Shadow," NY Times (4/30/13):

... In his Second Inaugural Address, Lincoln said he feared God would will the war to continue “until every drop of blood drawn with the lash shall be paid by another drawn with the sword.” This reckoning of the value of slaves in blood and treasure raises an important, though too frequently overlooked, question. What was the role of slavery in American economic development?

The most familiar answer to that question is: not much. By most accounts, the triumph of freedom and the birth of capitalism are seen as the same thing. The victory of the North over the South in the Civil War represents the victory of capitalism over slavery, of the future over the past, of the factory over the plantation. In actual fact, however, in the years before the Civil War, there was no capitalism without slavery. The two were, in many ways, one and the same.

...Between 1803 and 1838, the United States, most famously personified by Andrew Jackson, fought a multifront war in the Deep South. In those years, the United States suppressed slave revolts and pacified whites still loyal to the European powers that had once controlled the region. These wars culminated in the ethnic cleansing of the Deep South. By the end of the 1830s, the Seminole, the Creek, the Chickasaw, the Choctaw and the Cherokee had all been “removed” to lands west of the Mississippi. Their expropriated land provided the foundation of the leading sector of the global economy in the first half of the 19th century.

In the 1830s, hundreds of millions of acres of conquered land were surveyed and put up for sale by the United States. This vast privatization of the public domain touched off one of the greatest economic booms in the history of the world up to that time. Investment capital from Britain, the Continent and the Northern states poured into the land market. “Under this stimulating process, prices rose like smoke,” the journalist Joseph Baldwin wrote in his memoir, “The Flush Times of Alabama and Mississippi.”

Without slavery, however, the survey maps of the General Land Office would have remained a sort of science-fiction plan for a society that could never happen. Between 1820 and 1860 more than a million enslaved people were transported from the upper to the lower South, the vast majority by the venture-capitalist slave traders the slaves called “soul drivers.” The first wave cleared the region for cultivation. “Forests were literally dragged out by the roots,” the former slave John Parker remembered in “His Promised Land.” Those who followed planted the fields in cotton, which they then protected, picked, packed and shipped — from “sunup to sundown” every day for the rest of their lives.

Eighty-five percent of the cotton Southern slaves picked was shipped to Britain. The mills that have come to symbolize the Industrial Revolution and the slave-tilled fields of the South were mutually dependent. Every year, British merchant banks advanced millions of pounds to American planters in anticipation of the sale of the cotton crop. Planters then traded credit in pounds for the goods they needed to get through the year, many of them produced in the North. “From the rattle with which the nurse tickles the ear of the child born in the South, to the shroud that covers the cold form of the dead, everything comes to us from the North,” said one Southerner. [Some specifics: British cotton imports were 12m pounds/year, 1790s and 588m lbs, 1850; exports of finished products grew from 40m sq yards to 2 billion per year in the same period; the cost of cotton goods was 1% in 1850 of what it had been, 1780s; before 1820s, it cost $5 to move 100 lbs cotton downriver from Louisville; in 1840, it cost 25 cents. In 1860, S cotton is 57% of all American exports. N farms export 5% of their output; S plantations export 75% of theirs. S cotton exports, 1860, are 50x the South's total cotton export of next 4 years.]

[According to lawyer, politician, and social theorist William Harper of South Carolina, "the Creator did not intend that every individual human being should be highly cultivated. It is better that a part should be fully and highly educated and the rest utterly ignorant."]

As slaveholders supplied themselves (and, much more meanly, their slaves) with Northern goods, the credit originally advanced against cotton made its way north, into the hands of New York and New England merchants who used it to purchase British goods. Thus were Indian land, African-American labor, Atlantic finance and British industry synthesized into racial domination, profit and economic development on a national and a global scale.

When the cotton crop came in short and sales failed to meet advanced payments, planters found themselves indebted to merchants and bankers. Slaves were sold to make up the difference. The mobility and salability of slaves meant they functioned as the primary form of collateral in the credit-and-cotton economy of the 19th century.

It is not simply that the labor of enslaved people underwrote 19th-century capitalism. Enslaved people were the capital: four million people worth at least $3 billion in 1860, which was more than all the capital invested in railroads and factories in the United States combined. [With inflation factored in, the Civil War cost the South between $5 and $8 billion. Had they accepted Lincoln's 1861 plan to buy all of their slaves and pay the cost with bonds, every slave could have been freed at market value, with enough left over to furnish 40 acres and a mule for every slave family and leave about $3-4 billion to promote freedmen's entrance into the market economy.] Seen in this light, the conventional distinction between slavery and capitalism fades into meaninglessness.

We are accustomed to reckoning the legacy of slavery in the United States in terms of black disadvantage. The centrality of slavery to the nation’s economic development, however, suggests that any calculation of the nation’s unpaid debt for slavery must include a measure of the wealth it produced, of advantage as well as disadvantage. The United States, as W. E. B. Du Bois wrote, was “built upon a groan.”

other measures of Southern distinctiveness:

1849-61 all Secretaries of War are Southerners, as was general in chief of army, 2 of 3 brigadier generals, and 40% of West Point alumni and army officers (South is c.30% of white population, so is overrepresented); 60%+ of volunteers in Mexican War from S (more than 4x per capita Northern volunteer rate); 7 of 8 military schools (excluding West Point and Annapolis) were in S. Dictionary of National Biography for the antebellum period contains 2x as many Southerners as Northerners; in arts, literature, medicine, education 2x as many Northerners; 3x as many N businessmen; 6x as many N engineers and inventors.

In 1860 slave states have half as high % of white kids in school, and school term c. 1/2 of N term. Per capita newspaper circulation 3x higher in N, library volumes/person in N 2x as high. 3x as many white illiterates in S as in N; including both races (remember, teaching slaves to read after Nat Turner is illegal), % of illiterates 7-8x higher in S.