Kansas-Nebraska Act

But “the sectional bargain collapsed with the passage of the Kansas-Nebraska Act in 1854,” Radan writes, nullifying the Missouri Compromise for the territories of Kansas and Nebraska, leaving states that emerged there “free to form and regulate their domestic institutions in their own way.”

In May 1854, just as the Kansas-Nebraska Act exploded in American politics, a man named Anthony Burns, who had escaped slavery in Virginia, was arrested and detained in Boston.

Or did it come in 1854, when the Kansas-Nebraska Act proposed to settle the question of whether those territories would permit slavery on the basis of “popular sovereignty,” meaning the voters would decide by referendum?

David W. Blight, a Yale historian and expert on the breakdown of American governance before the Civil War, spoke of the hollowing of the political center in the mid-19th century and, after the passage of the Kansas-Nebraska Act of 1854, congressional paralysis.

Lincoln was pushed to modify his original position by proslavery Southerners who asserted an ever more aggressive agenda of slavery expansion in the 1850s, as evidenced in the Kansas-Nebraska Act and the Dred Scott decision, both of which invalidated the 1820 Missouri Compromise.