[Restorer]

But according to this site, the first sovereign state to abolish slavery was the Free and Independent State of Vermont, which occurred when Vermont adopted its Constitution of 1777.

Britain abolished slavery in Britain in 1772 with the famous Mansfield (?) decision. Thereafter, any slave who touched the soil of the UK became a free man.

[billbears]

Slavery in Britain yes but not her colonies. The 1830s law was necessary for that

[cookcounty]

The US international SLAVE TRADE was abolished by the US Constitution ( which made it effective 20 tears after ratification --- therefore the "1808" date).