“Slavery is now no where more patiently endured, than in countries once inhabited by the zealots of liberty.”

Journal of John Quincy Adams (11 December 1838),
Context: The conflict between the principle of liberty and the fact of slavery is coming gradually to an issue. Slavery has now the power, and falls into convulsions at the approach of freedom. That the fall of slavery is predetermined in the counsels of Omnipotence I cannot doubt; it is a part of the great moral improvement in the condition of man, attested by all the records of history. But the conflict will be terrible, and the progress of improvement perhaps retrograde before its final progress to consummation.

Source: Artefactos

Source: Why We Can't Wait

Part II, section 1.
Evangeline: A Tale of Acadie (1847)

Source: Clockwork Princess

1880s, Personal Memoirs of General U. S. Grant (1885)
Context: Slavery was an institution that required unusual guarantees for its security wherever it existed; and in a country like ours where the larger portion of it was free territory inhabited by an intelligent and well-to-do population, the people would naturally have but little sympathy with demands upon them for its protection. Hence the people of the South were dependent upon keeping control of the general government to secure the perpetuation of their favorite institution. They were enabled to maintain this control long after the States where slavery existed had ceased to have the controlling power, through the assistance they received from odd men here and there throughout the Northern States. They saw their power waning, and this led them to encroach upon the prerogatives and independence of the Northern States by enacting such laws as the Fugitive Slave Law. By this law every Northern man was obliged, when properly summoned, to turn out and help apprehend the runaway slave of a Southern man. Northern marshals became slave-catchers, and Northern courts had to contribute to the support and protection of the institution.

Variant: Because paper has more patience than people.
Source: The Diary of a Young Girl

Remarks on the Republican platform (1860)
Context: Suddenly, and without the least necessity or provocation, the country was startled with a proposition to reopen the slavery agitation in a more aggravated form than ever before. The Kansas-Nebraska bill was introduced by Senator Douglas, Chairman of the Committee on Territories, sustained as a Democratic measure by President Pierce, and adopted by Democratic and Southern Whig votes. The bond of peace agreed to in 1850-51-52, was broken, and broken, too, by the very men who had pledged themselves not again to agitate the slavery question. … After a severe struggle, which threatened the integrity of the Union, Congress finally passed laws settling these questions; and the Government and the people for a time seemed to acquiesce in that compromise as a final settlement of this exciting question; and it is exceedingly to be regretted that mistaken ambition, or the hope of promoting a party triumph, should have tempted any one to raise this question again. But in an evil hour this Pandora's box was again opened by what I conceive to be an unjustifiable attempt to force slavery into Kansas by a repeal of the Missouri compromise, and the floods of evils now swelling and threatening to overthrow the Constitution, and sweep away the foundation of the Government itself, and deluge this land with fraternal blood, may all be traced to this unfortunate act.

Balsamo the Magician (or The Memoirs of a Physician) by Alex. Dumas (1891)