Important and exciting as was the war question of 1812, it never so alarmed the sagacious statesmen of the country for the safety of the Republic as afterward did the Missouri question.  This sprang from that unfortunate source of discord—­negro slavery.  When our Federal Constitution was adopted, we owned no territory beyond the limits or ownership of the States, except the territory northwest of the River Ohio and east of the Mississippi.  What has since been formed into the States of Maine, Kentucky and Tennessee, was, I believe, within the limits of or owned by Massachusetts, Virginia, and North Carolina.  As to the Northwestern Territory, provision had been made even before the adoption of the Constitution that slavery should never go there.  On the admission of States into the Union, carved from the territory we owned before the Constitution, no question, or at most no considerable question, arose about slavery—­those which were within the limits of or owned by the old States following respectively the condition of the parent State, and those within the Northwest Territory following the previously made provision.  But in 1803 we purchased Louisiana of the French, and it included with much more what has since been formed into the State of Missouri.  With regard to it, nothing had been done to forestall the question of slavery.  When, therefore, in 1819, Missouri, having formed a State constitution without excluding slavery, and with slavery already actually existing within its limits, knocked at the door of the Union for admission, almost the entire representation of the non-slaveholding States objected.  A fearful and angry struggle instantly followed.  This alarmed thinking men more than any previous question, because, unlike all the former, it divided the country by geographical lines.  Other questions had their opposing partisans in all localities of the country and in almost every family, so that no division of the Union could follow such without a separation of friends to quite as great an extent as that of opponents.  Not so with the Missouri question.  On this a geographical line could be traced, which in the main would separate opponents only.  This was the danger.  Mr. Jefferson, then in retirement, wrote: 

“I had for a long time ceased to read newspapers or to pay any attention to public affairs, confident they were in good hands and content to be a passenger in our bark to the shore from which I am not distant.  But this momentous question, like a firebell in the night, awakened and filled me with terror.  I considered it at once as the knell of the Union.  It is hushed, indeed, for the moment.  But this is a reprieve only, not a final sentence.  A geographical line coinciding with a marked principle, moral and political, once conceived and held up to the angry passions of men, will never be obliterated, and every irritation will mark it deeper and deeper.  I can say with conscious truth that there is not a man on earth who would sacrifice more than I would to relieve us from this heavy reproach in any practicable way.