Your question is ridiculous, absurd, obscene and not subject to direct answer.
It's the equivalent of "when did you stop beating your wife."
You want to redefine good as evil and evil as good, because that's your job as a propagandist.
Regardless of how you want to spin it, the fact remains that by 1791, immediate or gradual abolition was the law in six Northern states, plus Maine and the Northwest Territories which became six more free-states, but no Southern state ever passed abolition laws before the Civil War.
DiogenesLamp: "I will say that the correct number of slave states in 1787 is "12."
And no more of that "I will gladly pay you Tuesday for a Hamburger today" crap about getting rid of slavery.
If you still have slavery, you are still a slave state."
If that were remotely true, then the US is still a "slave nation" today, since we are told that among the millions of illegal-but-welcomed-by-Democrats immigrants are many who've sold themselves, or been sold by others, into slavery to pay for past debts and their transportation or settlement here.
Plus, many people redefine capitalist workers as "slaves" of "the system" and so on and so on -- it's all hyperbole and nonsense.
The historical fact remains, all your propaganda work notwithstanding, that once a Northern state had passed laws gradually abolishing slavery, it considered itself a "free-state" and was also considered "free" by Southern slave-states.
No Southerner in, say, 1850, distinguished between Northern states which had zero slaves and those which still had the occasional old servants not officially freed.
Even in the 1787 Constitutional Convention, there was no doubt as to which states supported slavery, and which states wanted to oppose it.
In nearly every Northern case, abolition was gradual, but also certain.