All that is true. Nevertheless, I present the views of Alexis de Tocqueville on the subject. Democracy in America is online. What follows is from chapter 18, in the section you can search for in that chapter. Search for Contrast between the left and the right bank of the Ohio. This is a long post, but I think the topic is interesting:
... in general, the colonies in which there were no slaves became more populous and more prosperous than those in which slavery flourished. The farther they went, the more was it shown that slavery, which is so cruel to the slave, is prejudicial to the master.There's much more in the book. It's well worth reading.
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Undulating lands extend upon both shores of the Ohio, whose soil affords inexhaustible treasures to the laborer; on either bank the air is equally wholesome and the climate mild, and each of them forms the extreme frontier of a vast state: that which follows the numerous windings of the Ohio upon the left is called Kentucky; that upon the right bears the name of the river. These two states differ only in a single respect: Kentucky has admitted slavery, but the state of Ohio has prohibited the existence of slaves within its borders. Thus the traveler who floats down the current of the Ohio to the spot where that river falls into the Mississippi may be said to sail between liberty and servitude; and a transient inspection of surrounding objects will convince him which of the two is more favorable to humanity.Upon the left bank of the stream [Kentucky] the population is sparse; from time to time one descries a troop of slaves loitering in the half-desert fields; the primeval forest reappears at every turn; society seems to be asleep, man to be idle, and nature alone offers a scene of activity and life.
From the right bank [Ohio], on the contrary, a confused hum is heard, which proclaims afar the presence of industry; the fields are covered with abundant harvests; the elegance of the dwellings announces the taste and activity of the laborers; and man appears to be in the enjoyment of that wealth and contentment which is the reward of labor.
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Upon the left bank [Kentucky] of the Ohio, labor is confounded with the idea of slavery, while upon the right bank [Ohio] it is identifies with that of prosperity and improvement; on the one side it is degraded, on the other it is honored. On the former territory no white laborers can be found, for they would be afraid of assimilating themselves to the Negroes; all the work is done by slaves; on the latter no one is idle, for the white population extend their activity and intelligence to every kind of employment. Thus the men whose task it is to cultivate the rich soil of Kentucky are ignorant and apathetic, while those who are active and enlightened either do nothing or pass over into Ohio, where they may work without shame.
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As the same causes have been continually producing opposite effects for the last two centuries in the British colonies of North America, they have at last established a striking difference between the commercial capacity of the inhabitants of the South and those of the North. At the present day it is only the Northern states that are in possession of shipping, manufactures, railroads, and canals.
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The influence of slavery upon the production of wealth must have been very imperfectly known in antiquity, as slavery then obtained throughout the civilized world, and the nations that were unacquainted with it were barbarians. And, indeed, Christianity abolished slavery only by advocating the claims of the slave; at the present time it may be attacked in the name of the master, and upon this point interest is reconciled with morality.
I've never had a problem with slavery being a part of America's history, I do have have to admit a bit of doubt on the judgment of the part of the buyers, though.