During the Secession Crisis between December 1860 and April 1861, there were voices on both sides calling for "peaceable separation", "peaceable dissolution," and "peaceable disunion" on both sides. One of the most powerful Northern voices on this matter was Horace Greeley, publisher and editor of the most widely read newspaper of the era, the New York Tribune. He was a longtime abolitionist and moderate Republican. "Let the erring sisters go in peace," he wrote in an editorial during the crisis.

There were many others in the North who took similar positions, and then in the South, there were some who did, too. In California, the state congressmen aligned with Breckinridge's Southern Democrats were led by Charles Lindley, who declared during the Cirisis :

"Let us have union if we can; peaceable dissolution if we must but conflict never."

But Lindley's speech pointed out the problems with "peaceable dissolution," because in the very next line he said, if the Union should be dissolved, why should California stay with the free states? He doesn't advocate that they should join the Confederates, either, but instead, California should establish a "Pacific nationality" all its own, as an independent country.

The issue facing everyone was what a "peaceable separation" would even entail. Greeley's stance in favor of it was only because it was preferable to compromise over Northern and Republican principles. At the top of column three of this newspaper page from February 4, 1861, you see an editorial reprinted from the Cincinnati Times which stated that Republicans not standing up for the electoral victory they just won, or worse, just letting the South go over an election they were not happy about, was going to have future ramifications that would doom the United States in the future to further dissolutions over political disagreements.

And the Southern political class wasn't really looking for "peaceable separation" as a first resort, either, as Lindley's speech makes clear. They wanted "compromise" what would entail the North recognizing the South's right to remain slave states forever and always and deny the North any constitutional ability to interfere with it, ever, which is what the "Corwin Amendment" to the Constitution attempted to do. They also wanted the North to cede some amount of Western land to become slave states, and any kind of "free soil" future for the West was a non-starter. The Republican Party refused to negotiate on such terms on either issue. So a "peaceable separation" really wasn't any more attainable than a compromise that kept the Confederate states within the Union, because those issues had to be resolved whether they stayed within the Union or not. As Constitutional scholar Nathan Dane had written thirty years earlier:

"If there shall ever be a separation...the immense property of the United States will be a bone of contention and with other causes, will in time bring on hot contention or war, or prove a separation far worse than compromise...Secession, not assented to, draws the sword."

In other words, it wasn't enough to just say, "Hey, let's go our separate ways." Division of U.S. property within the Southern states, division of U.S. property out West, the division of national debts, treaties over the recovery of escape slaves, treaties over control of the Mississippi River that interior Northern states depended on for commerce, and so on and so on...These were all issues that a "peaceable separation" couldn't address any better than a compromise keeping the South part of the United States could.

In the few months between the time secession began and the time Fort Sumter was attacked, the Republican Party's majority position, then, was not to compromise on the South's terms in regards to slavery's Western expansion, fugitive slave laws, and more, while the South's majority position was not to allow any of these Republican positions be allowed to stand.

South Carolina opened fire on Fort Sumter, and pretty much immediately, most "moderates" were pushed one way or the other, as this May 1861 editorial from the Boston Daily Advertiser makes clear. Greeley and people like him dropped calls for "peaceable separation" and began calling for the U.S. to stand united against a movement that would destroy the Union entirely. Southerners who had called for "peaceable separation" now wanted to win that separation through war, so they could force the North to assent to all the positions on slave law that concerned the South.

Politicians in the North who continued to advocate "peaceable dissolution" very quickly found themselves in the minority. The more powerful voices in the North opposing the war did it more on the terms of "Let the South back into the Union and give them everything they want," rather than, "Let them go," because that would also give them everything they wanted anyway. There were "Copperheads"/"Peace Democrats" like Clement Vallandigham of Ohio who would have gladly taken a "peaceable separation" if it meant the end to the war. But he, and many others, lost re-election in 1862, as those voices became less popular. In fact, he was deported to the South for violating an ordinance in Ohio that forbade sympathizing with the enemy, after giving a pro-Southern speech in mid-1863. He was subject to a military trial, and then deported to the Confederacy, where he immediately surrendered as a prisoner of war, considering himself a U.S. citizen. He was then allowed to escape, made his way to Canada by an ocean voyage, and then ran for governor of Ohio from his place of exile. He lost in a landslide, getting less than 40% of the vote, though that still accounted for 187,000 votes of Ohioans.

But again, once the war started, Vallandigham and people the types of people who supported him once the war broke out tended to want the North to compromise on the South's terms that would allow the South to rejoin the Union. "Peaceable separation" was secondary since it wasn't seen as any more attainable than reunion, despite basically requiring the same set of compromises either way. So other Copperheads like Franklin Pierce tended to play up national unity in advocating for the acceptance of the South's demands, as a more achievable peace than disunion was.