A couple of years ago, a friend mentioned to me that 80 percent of her son's books featured African American characters. My own children's bookshelves were not nearly that diverse. This gave me pause because I had not done nearly as good a job as seeking out books for my children. They have (and had) hundreds of books, but I had not made the extra effort to diversify.
So I began to do it. And now, at the library and in book stores, I pick up books featuring African Americans, even when they don't. So our collection looks better and they see themselves in more books. But I'm always looking for more. Now, particularly, chapter books for my oldest child that feature boys of African descent.
He has read quite a few nonfiction titles about us, including titles that talk about slavery. So he knows about slavery and segregation.
Now I've found a list of some of the slavery titles in kids literature. Here's a link to that list from Carol Hurst's web site.