Massachusetts, but it peaked in the 18th century.
MA has actually improved significantly over time. It started out as a place run by insane religious fanatics who literally executed people for holding different beliefs or "practicing witchcraft," among other backwards and heinous practices.
That's certainly one view of the Puritans that exists in the popular imagination, but not one I or most scholars would agree with. Yes the witch trials were bad, but the good they did for the cause of liberty far outweighs the bad. Simply put, Massachusetts Bay was the most democratic colony (later state) in America. Its elections were fair and often, its legislatures were filled with as many small farmers as rich merchants, and its land was distributed fairly equally among the population. This was in stark contrast to the American South, a strict top-down hierarchical society dominated by aristocratic large plantation owners. It's always struck me as ironic that the Jeffersonian vision of an agrarian republic of virtuous small farmers was best realized in rural New England, typified by farmer's sons of modest stock like John Adams, while it was perhaps worst realized in his own state of Virginia, home to planter elites like Jefferson himself.
Now, why do I say Massachusetts peaked in the 18th century? That was when the
city-state of Boston was at its height, a mercantile powerhouse largely able to pursue an independent course within both the British Empire and the United States. It was a time when Massachusetts was a hotbed of rebellion against tyranny, be it in the form of King George III or the slave power. The Puritan ethos of resistance was still alive and well in the state when men dressed as Indians dumped tons of British tea into the Boston Harbor. So was it when Daniel Shays and his farmers took up arms against oppressive taxes. But at some point in the 19th century, that changed. As much as I hate to admit it, the Puritan spirit of the state was lost and replaced by a sort of entrenched conservatism, the very thing Massachusetts was founded in opposition to. It's debatable when the change happened, but that it happened is undeniable. The book review I linked to marks 1854 as the end of Boston, the year it failed to protect Anthony Burns from slave catchers, while the book itself places the end date at 1865. Regardless of the exact date, it is a great American tragedy that Massachusetts became the very thing it had fought to destroy.
Massachusetts, but it peaked in the 18th century.
MA has actually improved significantly over time. It started out as a place run by insane religious fanatics who literally executed people for holding different beliefs or "practicing witchcraft," among other backwards and heinous practices.
Yeah, it's truly horrible what Catholic immigration can do to a place 
For many years Massachusetts was arguably the most racially progressive place in America. In 1783 it was one of the first states to abolish slavery. In the 19th century, Boston was
the leading centre of the abolitionist movement. But by the 20th century, the city had gained a reputation for notorious racism against black people. The major demographic change that had occurred in these years, of course, was massive Irish immigration. As has been described by North Carolina Yankee in our historical discussions, the urban Irish were drawn to the racist appeals of the Democratic Party. Given this, I think it is highly likely that the immigration of Irish people was largely responsible for the increase of anti-black racism in Boston. That's not to say that nativist campaigns against the Irish were justified, of course, often being based upon racism themselves. But it is to say that Catholic immigration had a definite effect on the place, and not an altogether positive one.
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