The challenge is to have slavery abolished in the USA by the year 1870 without a civil war, or even a serious discussion of secession. Bonus if you can create a relatively racially equal society by 1890, with a strong protection of civil rights. Ideally you can do it without British interference, but that may be nigh impossible.
Rule:
The POD must be later than 1799, and cannot include the US totally losing the War of 1812.