Historical Developments that led to the Ending of Slavery in the US

[Althusser]

What are the historical developments that led to the ending of slavery in the U.S.

Obviously it wasn't some surge of human compassion.

What material interests did what section of the ruling class have to gain with the outlawing of slavery in the U.S.?

[Invader Zim]

Well, to answer that you have to look back to the abolition of the slave trade, by both Britain and the US, in 1807-08. That was the real nail in the coffin of slavery, though various US states had already abolished slavery and the Southern States clung onto the institution for another 50 years there abouts. Really, though, the institution was doomed and would have been abolished sooner rather than later with or without the Civil War.

But in answer to your question, the basis for the abolition of slavery has been a long debated topic. As you do, there is, or rather was, a strand of the historiography championed by the likes of Eric Williams (http://archive.org/details/capitalismandsla033027mbp) which emphasised shifting material economic structures which rendered slavery unprofitable. However, by the 1970s this theory was heavily undermined by new research which showed that slavery and the slave trade remained highly profitable (http://books.google.co.uk/books/about/Econocide.html?id=Y3GiXfJSuK0C&redir_esc=y). Subsequently historians have been looking into other factors, related to the rise of the ideals developed during the enlightenment while others have convincingly shown that abolitionism was linked to the shifting religious ideas (http://books.google.co.uk/books?id=mmraAAAAMAAJ&q=roger+anstey&dq=roger+anstey&hl=en&sa=X&ei=kJAgUoGiO_Gd7gbvy4HQDQ&ved=0CDYQ6AEwAQ).