Slavery in the North
Regarding slavery in the north, I have two books you might want to read.
About four years ago, The New York Historical Society had a landmark exhibit, "Slavery in New York".  The book published about the exhibit is titled the same and published in conjunction with The New York Historical Society.  It most likely can be purchased from them.  Most interesting and certainly informative for "those people".
Another book titled "Complicity":  How the North Promoted, Prolonged and Profited from Slavery, by Ann Farrow, Joel Lang and Jennifer Frank is most enlightening.  I believe one of the authors has an ancestor who was a slave.
It is high time folks realized that slaves were in the north as well as the south.  The New Englanders became rich off the slave trade.  "Those people" certainly have no right to be self-righteous and condemn the few who owned slaves in the south.  
A fourteenth generation Southerner!!
Namuni Hale Young