Such was the situation when the application of Missouri for admission as a state in 1819 presented to Congress the whole question of slavery beyond the Mississippi, where freedom and slavery had found a new fighting-ground. East of the Mississippi the Ohio was a natural dividing-line; farther west there appeared no obvious boundary between slavery and freedom. By a natural process of selection, the valleys of the western tributaries of the Mississippi, as far north as the Arkansas and Missouri, in which slaves had been allowed while it was a part of French and Spanish Louisiana (no restraints having been imposed by Congress), received an increasing proportion of the slave-holding planters. It would, in the ordinary course of events, become the area of slave states.

The struggle began in the House of Representatives, when the application of Missouri for statehood was met by an amendment, introduced by Tallmadge of New York, February 13, 1819, [Footnote: Annals of Cong., 15 Cong., 2 Sess., I., 1170.] providing that further introduction of slavery be prohibited and that all children born within the state after admission should be free at the age of twenty-five years. [Footnote: See amended form in House Journal, 15 Cong., 2 Sess., 272.] Tallmadge had already showed his attitude on this question when in 1818 he opposed the admission of Illinois under its constitution, which seemed to him to make insufficient barriers to slavery. Brief as was the first Missouri debate, the whole subject was opened up by arguments to which later discussion added but little. The speaker, Henry Clay, in spite of the fact that early in his political career he had favored gradual emancipation in Kentucky, led the opposition to restriction. His principal reliance was upon the arguments that the evils of slavery would be mitigated by diffusion, and that the proposed restriction was unconstitutional. Tallmadge and Taylor, of New York, combated these arguments so vigorously and with such bold challenge of the whole system of slavery in new territories, that Cobb, of Georgia, declared, "You have kindled a fire which all the waters of the ocean cannot put out, which seas of blood can only extinguish." [Footnote: Annals of Cong., 15 Coneg., 2 Sess., I., 1204.]

The first clause of Tallmadge's motion was carried (February 16, 1819) by a vote of 87 to 76, and the second by 82 to 78. [Footnote: Ibid., 1214.] Taylor was emboldened to offer (February 18) to the bill for the organization of Arkansas territory an amendment by which slavery should be excluded, whereupon McLane, of Delaware, tentatively proposed that a line should be drawn west of the Mississippi, dividing the territories between freedom and slavery. Thus early was the whole question presented to Congress. In the Senate, Tallmadge's amendment was lost (February 27) by a vote of 22 to 16, several northern senators adhering to the south; and Congress adjourned without action. [Footnote: But Arkansas was organized as a territory without restriction.]

The issue was then transferred to the people, and in all quarters of the Union vehement discussions took place upon the question of imposing an anti-slavery restriction upon Missouri. Mass-meetings in the northern states took up the agitation, and various state legislatures, including Pennsylvania, New York, New Jersey, Ohio, and even the slave state of Delaware, passed resolutions with substantial unanimity against the further introduction of slaves into the territories of the United States, and against the admission of new slave states. Pennsylvania, so long the trusted ally of the south, invoked her sister states "to refuse to covenant with crime" by spreading the "cruelties of slavery, from the banks of the Mississippi to the shores of the Pacific." From the south came equally insistent protests against restriction. [Footnote: Niles' Register, XVII., 296, 307, 334, 342-344, 395. 399. 400, 416; Ames, State Docs. on Federal Relations, No. 5, p. 4.]

No argument in the debate in 1819 was more effective than the speech of Rufus King in the Senate, which was widely circulated as a campaign document expressing the northern view. King's antislavery attitude, shown as early as 1785, when he made an earnest fight to secure the exclusion of slavery from the territories, [Footnote: McLaughlin, Confederation and Constitution (Am. Nation, X.), chap. vii.] was clearly stated in his constitutional argument in favor of restriction on Missouri, and his speech may be accepted as typical. [Footnote: Niles' Register, XVII., 215; King, Life and Corresp. of King, VI., 690.] But it was also the speech of an old-time Federalist, apprehensive of the growth of western power under southern leadership. He held that, under the power of making all needful rules and regulations respecting the territory and other property of the United States, Congress had the right to prohibit slavery in the Louisiana purchase, which belonged to the United States in full dominion. Congress was further empowered, but not required, to admit new states into the Union. Since the Constitution contained no express provision respecting slavery in a new state, Congress could make the perpetual prohibition of slavery a condition of admission. In support of this argument, King appealed to the precedent of the Ordinance of 1787, and of the states of Ohio, Indiana, and Illinois, all admitted on the conditions expressed in that ordinance. In admitting the state of Louisiana in 1812, a different group of conditions had been attached, such as the requirement of the use of the English language in judicial and legislative proceedings.

The next question was the effect of the Louisiana treaty, by which the United States had made this promise: "The inhabitants of the ceded territory shall be incorporated in the Union of the United States, and admitted as soon as possible, according to the principles of the Federal constitution, to the enjoyment of all the rights, advantages and immunities of citizens of the United States; and in the mean time they shall be maintained and protected in the free enjoyment of their liberty, property and the religion which they profess." [Footnote: U. S. Treaties and Conventions, 332.] King contended that, by the admission of Missouri to the Union, its inhabitants would obtain all of the "federal" rights which citizens of the United States derived from its Constitution, though not the rights derived from the constitutions and laws of the various states. In his opinion, the term PROPERTY did not describe slaves, inasmuch as the terms of the treaty should be construed according to diplomatic usage, and not all nations permitted slavery. In any case, property acquired since the territory was occupied by the United States was not included in the treaty, and, therefore, the prohibition of the future introduction of slaves into Missouri would not affect its guarantees.

Could Missouri, after admission, revoke the consent to the exclusion of slavery under its powers as a sovereign state? Such action, King declared, would be contrary to the obligations of good faith, for even sovereigns were bound by their engagements. Moreover, the judicial power of the United States would deliver from bondage any person detained as a slave in a state which had agreed, as a condition of admission, that slavery should be excluded.

Having thus set forth the constitutional principles, King next took up the expediency of the exclusion of slavery from new states. He struck with firm hand the chord of sectional rivalry in his argument against the injustice to the north of creating new slave-holding states, which would have a political representation, under the "federal ratio," not possessed by the north. Under this provision for counting three-fifths of the slaves, five free persons in Virginia (so he argued) had as much power in the choice of representatives to Congress and in the appointment of presidential electors as seven free persons in any of the states in which slavery did not exist. The disproportionate power and influence allowed to the original slave-holding states was a necessary sacrifice to the establishment of the Constitution; but the arrangement was limited to the old thirteen states, and was not applicable to the states made out of territory since acquired. This argument had been familiar to New England ever since the purchase of Louisiana. Finally, he argued that the safety of the Union demanded the exclusion of slavery west of the Mississippi, where the exposed and important frontier needed a barrier of free citizens against the attacks of future assailants.

To the southern mind, King's sectional appeal unblushingly raised the prospect of the rule of a free majority over a slave-holding minority, the downfall of the ascendancy so long held by the south, and the creation of a new Union, in which the western states should be admitted on terms of subordination to the will of the majority, whose power would thus become perpetual. [Footnote: King, Life and Corresp. of King, VI., 205, 267, 279, 288, 329, 339-344, 501; Jefferson, Writings (Ford's ed.), X., 162, 172, 280; Tyler, Tylers, I., 316.]

When the next Congress met, in December, 1819, the admission of Alabama was quickly completed; and the House also passed a bill admitting Maine to the Union, Massachusetts having agreed to this division of the ancient commonwealth, on condition that consent Congress should be obtained prior to March 4, 1820. The Senate, quick to see the opportunity afforded by the situation, combined the bill for the admission of Maine with that for the unrestricted admission of Missouri, a proposition carried (February 16, 1820) by a vote of 23 to 21. Senator Thomas, who represented Illinois, which, as we have seen, was divided in its interests on the question of slavery, and who, as the vote showed, could produce a tie in the Senate, moved a compromise amendment, providing for the admission of Missouri as a slave state and for the prohibition of slavery north of 36 degrees 30' in the rest of the Louisiana purchase; and on the next day his amendment passed the Senate by a vote of 34 to 10.