From that year the slave interests of the South rose in market value, and its industrial system assumed unexpected importance in the economic world.  The increased production of cotton led directly to increased demand for slave labor and slave soil.  The increased demand for slave labor the Constitutional provision relating to the African slave trade operated in part to satisfy.  The increased demand for slave soil was likewise satisfied by the cession to the United States by Georgia and North Carolina of the Southwest Territory, with provisos practically securing it to slavery.  Out of this new national territory were subsequently carved the slave States of Tennessee, Mississippi, and Alabama.

Slave soil unlike free soil, is incapable of sustaining a dense population.  Slave labor calls for large spaces within which to multiply and prosper.  The purchase of Louisiana and the acquisition of Florida met this agrarian necessity on the part of the South.  Immense, unsettled areas thus fell to the lot of the slave system at the crisis of its material expansion and prosperity.  The domestic slave-trade under the impetus of settling these vast regions according to the plantation principle, became an enormous and spreading industry.  The crop of slaves was not less profitable than the crop of cotton.  A Southern white man had but to buy a score of slaves and a few hundred acres to get “rich beyond the dreams of avarice.”  So at least calculated the average Southern man.

This revival of slavery disappointed the humane expectation of its decline and ultimate extinction entertained by the founders of the republic.  It built up instead a growing and formidable slave class, and interest in the Union.  With the rise of giant slave interests, there followed the rise of a power devoted to their encouragement and protection.

Three far-reaching concessions the slave States obtained in the convention of 1787, viz., the right to import slaves from Africa until 1808; the rendition of fugitive slaves escaping into the free States, and the three-fifths slave representation clause of the Constitution—­all of which added vastly to the security and value of this species of property, and as a consequence contributed to the slave revival.

The equality of the States in the upper branch of the National Legislature, taken in connection with the right of the slave States to count five slaves as three freemen in the apportionment of representatives to the lower House of Congress, gave the Southern section an almost immediate ascendency in the Federal Government.  To the South was thus opened by an unexpected combination of circumstances a wide avenue for the acquisition of fabulous wealth, and to Southern public men an incomparable arena for the exercise of political abilities and leadership.  An institution, which thus ministered to two of the strongest passions of mankind—­avarice and ambition—­was certain to excite the most intense attachment.