Elliot, Zetta. (2008). A Wish After Midnight. ?, Self-published?
The easy way to describe A Wish After Midnight is that it's a YA version of Octavia Butler's _Kindred_. I mean that as a compliment by the way.
Genna lives in Brooklyn. In the first half of the novel we see through her eyes all the threats that Black ghetto families face. Under the pressure of poverty and low expectations her family is disintegrating, and Genna's chances of getting up and out are diminished with every attempt she makes to help her mother. Her own confidence however is increased when she meets a Rastafarian boy called Judah.
In the second half, Genna finds herself flung back into 1863 Brookly, badly injured although she can't remember how. She is taken in by free black folk and settles down to the indignities of being Black in America in 1863. Later, Judah arrives, but he has been sold into slavery and is far willing to accept the hard scrabble comfort of freedom. The book ends with the draft riots, and a place for a sequel.
This really is rather a good book: the pre time travel section is too long for my tastes, but it's exploration of Genna's life is complex and demonstrates the degree to which racism is held together by many institutional structures. Once in the past the book really takes off: the racism and prejudice of white northerners is given short shrift, the ways in which white immigrants and blacks are played off against each other is dealt with very well, the compromised expectations of many people are depicted well, and the casual prejudice of the well meaning is displayed.