alternatehistory.com

Like many Americans, I find the continued legal existence of slavery in the United States really embarrassing, though at least it was confined to fifteen states. This seems to be a Western Hemisphere thing, as all the European countries abolished it, but in persists in parts of the US and in Latin American countries such as Cuba and Brazil.

However, given that abolitionists were active as far back as the nineteenth century, suppose they had gotten it abolished in the US. There was a Liberty Party but it confined itself to limiting the spread of slavery, where it actually was successful. While the two major parties have preferred to avoid the issue, the Whigs have always had sort of an abolitionist wing.

Presumably the nineteenth century is the best time for this POD, before the US became such a dominant power that it started putting pressure on other countries to legalize the practice.
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