“One hundred years after the Declaration that 'all men are created equal,' there began to gather in Newport a colony of the rich, determined to show that some Americans were conspicuously more equal than others.”

1850s, Speech at Peoria, Illinois (1854)
Context: Little by little, but steadily as man's march to the grave, we have been giving up the OLD for the NEW faith. Near eighty years ago we began by declaring that all men are created equal; but now from that beginning we have run down to the other declaration, that for SOME men to enslave OTHERS is a “sacred right of self-government.” These principles can not stand together. They are as opposite as God and mammon; and whoever holds to the one, must despise the other. [... ] Let no one be deceived. The spirit of seventy-six and the spirit of Nebraska, are utter antagonisms; and the former is being rapidly displaced by the latter.

Letter to longtime friend and slave-holder Joshua F. Speed (24 August 1855)
1850s, Letter to Joshua F. Speed (1855)
Context: You enquire where I now stand. That is a disputed point. I think I am a whig; but others say there are no whigs, and that I am an abolitionist. When I was at Washington I voted for the Wilmot Proviso as good as forty times, and I never heard of any one attempting to unwhig me for that. I now do more than oppose the extension of slavery.
I am not a Know-Nothing. That is certain. How could I be? How can any one who abhors the oppression of negroes, be in favor of degrading classes of white people? Our progress in degeneracy appears to me to be pretty rapid. As a nation, we began by declaring that "all men are created equal." We now practically read it "all men are created equal, except negroes." When the Know-Nothings get control, it will read "all men are created equal, except negroes, and foreigners, and catholics." When it comes to this I should prefer emigrating to some country where they make no pretence of loving liberty — to Russia, for instance, where despotism can be take pure, and without the base alloy of hypocracy [sic].

Sixth Lincoln-Douglas debate https://cwcrossroads.wordpress.com/2011/01/18/race-and-slavery-north-and-south-some-logical-fallacies/#comment-47553, (13 October 1860), Quincy, Illinois
1860s
Context: You know that in his Charleston speech, an extract from which he has read, he declared that the negro belongs to an inferior race; is physically inferior to the white man, and should always be kept in an inferior position. I will now read to you what he said at Chicago on that point. In concluding his speech at that place, he remarked, 'My friends, I have detained you about as long as I desire to do, and I have only to say let us discard all this quibbling about this man and the other man-this race and that race, and the other race being inferior, and therefore they must be placed in an inferior position, discarding our standard that we have left us. Let us discard all these things, and unite as one people throughout this land until we shall once more stand up declaring that all men are created equal'. Thus you see, that when addressing the Chicago Abolitionists he declared that all distinctions of race must be discarded and blotted out, because the negro stood on an equal footing with the white man; that if one man said the Declaration of Independence did not mean a negro when it declared all men created equal, that another man would say that it did not mean another man; and hence we ought to discard all difference between the negro race and all other races, and declare them all created equal.

Attributed

Delaware State Republican Dinner, 8 April 1995
1995

This they said, and this meant. They did not mean to assert the obvious untruth, that all were then actually enjoying that equality, nor yet, that they were about to confer it immediately upon them. In fact they had no power to confer such a boon. They meant simply to declare the right, so that the enforcement of it might follow as fast as circumstances should permit. They meant to set up a standard maxim for free society, which should be familiar to all, and revered by all; constantly looked to, constantly labored for, and even though never perfectly attained, constantly approximated, and thereby constantly spreading and deepening its influence, and augmenting the happiness and value of life to all people of all colors everywhere. The assertion that "all men are created equal" was of no practical use in effecting our separation from Great Britain; and it was placed in the Declaration, nor for that, but for future use. Its authors meant it to be, thank God, it is now proving itself, a stumbling block to those who in after times might seek to turn a free people back into the hateful paths of despotism. They knew the proneness of prosperity to breed tyrants, and they meant when such should re-appear in this fair land and commence their vocation they should find left for them at least one hard nut to crack. I have now briefly expressed my view of the meaning and objects of that part of the Declaration of Independence which declares that "all men are created equal".
1850s, Speech on the Dred Scott Decision (1857)

Variant: All animals are equal, but some animals are more equal than others.
Source: Animal Farm

In Defense of Emma Goldman and the Right of Expropriation (1893)
Context: Humanity can not be made equal by declarations on paper. Unless the material conditions for equality exist, it is worse than mockery to pronounce men equal. And unless there is equality (and by equality I mean equal chances for every one to make the most of himself) unless, I say, these equal chances exist, freedom, either of thought, speech, or action, is equally a mockery.

Source: The Visitor (2002), Ch. 4 : the cooper, p. 40