When the Federal Convention assembled at Philadelphia in May 1787 it speedily became evident that slavery, or rather the division of the Union into a free and a slaveholding sec tion, was an obstacle to the work. Following the suggestion of Mr. Madison, that it was °wrong to admit in the Constitution the idea of property in men," the Convention scrupulously avoided using the words slave and slavery in the final document, but six clauses in the final draft distinctly refer to that institution.
1. The apportionment of direct taxes °shall be determined by adding to the whole number of free persons . . . three-fifths of all other per sons." This clause was the result of a long and bitter controversy. As Gerry of Massachu setts put it, °why should blacks who are prop erty in the South, be in the rule of representa tion more than cattle and horses in the North ?" ; while Pinckney of South Carolina thought that in apportionment °the blacks ought to stand on an equality with the whites." 2. °The migration or importation of such persons as any States now existing shall think proper to admit, shall not be prohibited by the Congress," prior to 1808. This clause of course related to the slave trade, complete control over which was for a time withheld from Congress; and the concession to the Northern States was part of a bargain by which they retained the right to pass navigation acts.
3. A clause relating to fugitives provided for the return of any person °held to service or labor in one State, under the laws thereof, es caping into another." 4. The citizens of each State shall be enti tled to the privileges and immunities of the citi zens in the several States,"— a clause afterward applied to, or claimed for, negroes.
5. °Congress shall have power to dispose of and make all needful rules and regulations re specting territory or other property belonging to the United States." This was the power under which the Northwest Ordinance of 1787 had prohibited slavery.
6. Congress shall have power to exercise exclusive legislation in all cases whatsoever, over such district (not exceeding 10 miles square) as may, by cession of particular States and the acceptance of Congress, become the seat of the government of the United States, and to exercise like authority over all places purchased by the consent of the legislature of the State in which the same shall be, for the erection of forts, magazines, arsenals, dockyards and other needful buildings.
The experiment was now fairly under way of carrying on a Federal government with three different principles as regarded human slavery, — freedom in the Northern States; slavery in the Southern; and a discretionary power over territorial slavery in the Federal government.
The difficulties of this situation were clearly shown when, in 1790, the abolition societies petitioned Congress to regulate the slave trade; and the House of Representatives passed resolu tions in which they expressly disavowed any power to regulate slavery within the States. Three years later Congress exercised its power over fugitive slaves by passing an act which provided that under the authority of the United States and on the certificate of any magistrate, a master or his agent might personally appre hend a slave escaped into a free State.
In 1789 Congress exercised its power to deal with slavery in the Territories by re-enacting the ordinance of 1787; but in 1798, on the organi zation of Mississippi Territory, the anti-slavery clause was omitted, and slavery was allowed to continue there. In 1801 the United States took over the District of Columbia and reaffirmed the pre-existing laws of Maryland, including harsh slave codes. The act for organization of the Territory of Illinois contained a clause which in 1820 was applied by the Missouri Compromise to the northern portion of the Louisiana Purchase. Meanwhile a long con tinued agitation in England against the slave trade resulted in an act against it in 1806. This example was helpful in the United States which, by Act of 7 March 1807, laid an absolute prohibition on the foreign slave trade which was enforced by additional acts of 1818 and 1820.
In 1821, on the final admission of Missouri, Congress insisted that a clause in the State Constitution prohibiting the incoming of free negroes should be withdrawn, because contrary to the citizenship clause.
In the 40 years from 1790 to 1830 the con ditions of slavery radically changed. In 1790 the census showed 700,000 slaves; in 1830 there were 2,000,000, in each case about one-third of the total population of the slave-holding com munities. The persistence of slavery was un expected for in 1790 it was dying out from want of profitable employment. When Eli Whitney invented the cotton gin for separating the seed from the fibre (1794) a profitable crop was opened up to slave labor. The product of cotton in 1800 was 210,526 bales, in 1830 1,038, 847 bales. It is a crop requiring cultivation during a considerable part of the year and adapted to rude labor in large gangs; it thus made slave labor profitable in the Gulf States, and furnished a market for the surplus slave population of the border slave States; hence all sections of the South had an economic interest in its continuance.