The Freedom Maze — Delia Sherman

Thirteen-year-old Sophie isn't happy about spending the summer of 1960 at her grandmother's old house in the bayou. Bored and lonely, she can't resist exploring the house's maze, or making an impulsive wish for a fantasy-book adventure with herself as the heroine. What she gets instead is a real adventure: a trip back in time to 1860 and the race-haunted world of her family's Louisiana sugar plantation. Here, President Lincoln's Emancipation Proclamation is still two years in the future and passage of the Thirteenth Amendment is almost four years away. And here, Sophie is mistaken, by her own ancestors, for a slave.