Read the passage. There is Missouri at this moment, with Illinois on the east and Nebraska on the west, all covering nearly the same spaces of latitude, and resembling each other in soil, climate, and productions. Mark now the contrast! By the potent efficacy of the ordinance of the Northwestern Territory, Illinois is now a free State, while Missouri has 87,422 slaves; and the simple question which challenges an answer is, whether Nebraska shall be preserved in the condition of Illinois, or surrendered to that of Missouri? Surely this cannot be treated lightly. But for myself, I am unwilling to measure the exigency of the prohibition by the number of persons, whether many or few, whom it may protect. Human rights, whether in a vast multitude or a solitary individual, are entitled to an equal and unhesitating support.

Sir, the proposition before you involves not merely the repeal of an existing law, but the infraction of solemn obligations originally proposed and assumed by the South, after a protracted and embittered contest, as a covenant of peace—with regard to certain specified territory therein described, namely: "All that territory ceded by France to the United States, under the name of Louisiana;" according to which, in consideration of the admission into the Union of Missouri as a slave State, slavery was forever prohibited in all the remaining part of this territory which lies north of 36° 30'. . . . In its stipulations for slavery, it was justly repugnant to the conscience of the North, and ought never to have been made; but it has on that side been performed. And now the unperformed outstanding obligations to freedom, originally proposed and assumed by the South, are resisted.

–The Landmark of Freedom. Speech of Hon. Charles Sumner, Against the Repeal of the Missouri Prohibition of Slavery North of 36° 30’,
in the Senate, February 21, 1854

In addition to legislative action, judicial action also contributed to rising sectional tensions. For example, the outcome of Dred Scott v. Sandford

overturned the Fugitive Slave Act and made it illegal to capture runaways.
held that legislative restriction of slavery’s expansion was unconstitutional.
established decisive federal supremacy over states’ rights with regard to slavery.
temporarily calmed sectional tensions through well-reasoned arguments in the majority opinion.