The Territory of Missouri, containing the old French colonies at and near St. Louis, had attained a population of 60,000, and was eager to be admitted as a State. She had made application in 1817, and now in 1819 it was proposed to authorize her to form a constitution. Arkansas was also being nursed as an applicant, and the prospective loss by the North and gain by the South of the balance of power caused the slavery question suddenly to flare up as a national issue. There were hot debates in Congress, emphatic resolutions by State legislatures, deep agitation among the whole people, and open threats by the South to dissolve the Union. Extreme Northern men insisted upon a restriction of slavery to be applied to both Missouri and Arkansas; radical Southern members contended that Congress had no power to impose any conditions on new States. The North had control of the House, the South of the Senate. A middle party thereupon sprang up, proposing to divide the Louisiana purchase between freedom and slavery by the line of 36 degrees 30', and authorizing the admission of Missouri with slavery out of the northern half. Fastening this proposition upon the bill to admit Maine as a free State, the measure was, after a struggle, carried through Congress (in a separate act approved March 6, 1820), and became the famous Missouri Compromise. Maine and Missouri were both admitted. Each section thereby not only gained two votes in the Senate, but also asserted its right to spread its peculiar polity without question or hindrance within the prescribed limits; and the motto, "No extension of slavery," was postponed forty years, to the Republican campaign of 1860. From this time forward, the maintenance of this balance of power,--the numerical equality of the slave States with the free,--though not announced in platforms as a party doctrine, was nevertheless steadily followed as a policy by the representatives of the South. In pursuance of this system, Michigan and Arkansas, the former a _free_ and the latter a _slave_ State, were, on the same day, June 15, 1836, authorized to be admitted. These tactics were again repeated in the year 1845, when, on the 3d of March, Iowa, a _free_ State, and Florida, a _slave_ State, were authorized to be admitted by one act of Congress, its approval being the last official act of President Tyler. This tacit compromise, however, was accompanied by another very important victory of the same policy. The Southern politicians saw clearly enough that with the admission of Florida the slave territory was exhausted, while an immense untouched portion of the Louisiana purchase still stretched away to the north-west towards the Pacific above the Missouri Compromise line, which consecrated it to freedom. The North, therefore, still had an imperial area from which to organize future free States, while the South had not a foot more territory from which to create slave States.