In 1858, Abraham Lincoln launched his campaign for the Senate seat from Illinois with his now famous “A House Divided” speech. While he did not predict disunion or civil war, Lincoln alluded to the country’s deep political divisions over slavery and concluded, “I do not expect the house to fall—but I do expect it will cease to be divided. It will become all one thing or all the other.” 

Even before what historians call the political crisis of the 1850s, the rise of an interracial abolition movement had encountered mob violence in the streets and gag rules in Congress. From then on, abolitionism in the United States was tied to civil liberties and the fate of American democracy itself. By the eve of the war, in 1861, most people in the northern free states felt that the democratic institutions of the country were being subverted. 

There are many Americans who feel the same way today. Some have pointed to the glaring, and growing, partisan divide in the US to conjure doomsday scenarios, including “civil war.” How does our own epoch of fierce political polarization compare to the decade that was rent over the issue of slavery before the Civil War? Predictions are often overwrought and historical analogies can be misleading, but the controversies that bedeviled that age and its legacies still haunt us. In certain ways, they foreshadow—or, perhaps, still condition—our own divided house.

In 1850, the passage of a draconian federal Fugitive Slave Law not only imperiled black freedom, but also threatened the rule of law and due process in the North. During the Kansas Wars of 1854–1861, which were, in hindsight, a dress rehearsal for the Civil War, proslavery ruffians from Missouri regularly invaded Kansas to steal territorial elections and push through the legalization of slavery—contrary to the wishes of a majority of the states’ inhabitants. Finally, the Democratic-controlled federal administration tried to force on Kansans a proslavery state constitution, representing the interests of just 10 percent of the territory’s population. That attempt failed, but even northern Democrats realized that the white man’s democracy could break down over slavery. 

The controversy also took a violent turn. Abetted by their state governments, southern slaveholders had long restricted freedom of speech and of the press, as well as prescribing medieval forms of punishment for those accused of advocating abolition, including public whippings and imprisonment. In 1837, a pro-slavery mob had murdered the abolitionist newspaper editor Elijah Lovejoy as he defended his press in Alton, Illinois. It shocked the North when, in 1856, the South Carolinian Congressman Preston Brooks caned the anti-slavery senator from Massachusetts, Charles Sumner, for giving an abolitionist speech. By that time, many northerners, especially abolitionists, were ready to respond in kind: there was open warfare in Kansas between emigrants from slave states and free states, and fugitive slave rebellions throughout the North to prevent the rendition of runaway slaves. Such conflicts culminated, famously, in the raid at Harper’s Ferry in 1859, John Brown’s attempt to start a slave rebellion. ...