http://www.slate.com/articles/life/the_history_of_american_slavery/2015/06/the_demographics_of_american_slavery_according_to_new_research_by_eric_foner.html

In our Slate Academy on the history of American slavery, we’re trying hard to be specific about the shape of slavery in the United States—to go beyond a simple mental image of shackles, cotton, and plantations, and give this history some much-needed depth. To that end, here are a few demographic facts I discovered while researching the series that made me reconsider my previous assumptions.