Negro slavery was introduced into all the English colonies of North America as a custom, and not under any warrant of law.  The enslavement of the negro race was simply a matter against which no white person chose to enter a protest, or make resistance, while the negroes themselves were powerless to resist or even protest.  In due course of time laws were passed by the Colonial Assemblies to protect property in negroes, while the home government, to the very last, actively protected and encouraged the slave trade to the colonies.  Negro slavery in all the colonies had thus passed from custom to law before the American Revolution broke out; and the course of the Revolution itself had little or no effect on the system.

From the beginning, it was evident that the course of slavery in the two sections, North and South, was to be altogether divergent.  In the colder North, the dominant race found it easier to work than to compel negroes to work:  in the warmer South, the case was exactly reversed.  At the close of the Revolution, Massachusetts led the way in an abolition of slavery, which was followed gradually by the other States north of Virginia; and in 1787 the ordinance of Congress organizing the Northwest Territory made all the future States north of the Ohio free States.  “Mason and Dixon’s line” and the Ohio River thus seemed, in 1790, to be the natural boundary between the free and the slave States.

Up to this point the white race in the two sections had dealt with slavery by methods which were simply divergent, not antagonistic.  It was true that the percentage of slaves in the total population had been very rapidly decreasing in the North and not in the South, and that the gradual abolition of slavery was proceeding in the North alone, and that with increasing rapidity.  But there was no positive evidence that the South was bulwarked in favor of slavery; there was no certainty but that the South would in its turn and in due time come to the point which the North had already reached, and begin its own abolition of slavery.  The language of Washington, Jefferson, Madison, Henry, and Mason, in regard to the evils or the wickedness of the system of slavery, was too strong to be heard with patience in the South of after years; and in this section it seems to have been true, that those who thought at all upon the subject hoped sincerely for the gradual abolition of slavery in the South.  The hope, indeed, was rather a sentiment than a purpose, but there seems to have been no good reason, before 1793, why the sentiment should not finally develop into a purpose.

All this was permanently changed, and the slavery policy of the South was made antagonistic to, and not merely divergent from, that of the North, by the invention of Whitney’s saw gin for cleansing cotton in 1793.  It had been known, before that year, that cotton could be cultivated in the South, but its cultivation was made unprofitable, and checked by the labor required to separate the seeds from the