Also, the United States was about 30+ years late to abolishing slavery, if you want to find the source of the abolitionist movement, it was not America. UK, and most of Europe had outlawed it MANY years before we did, well before we brought it to the courts.
UK abolished slavery in 1833 https://en.wikipedia.org/wiki/Slavery_Abolition_Act_1833
US abolished slavery in 1865 http://www.history.com/this-day-in-history/slavery-abolished-in-america