Ashes (Seeds of America #3) by Laurie Halse Anderson

That’s the question that burns in Isabel’s mind as she and Curzon forge on through chaos and fear toward the dream that’s kept them alive for so many years: freedom. But her dream of living not as a “runaway” but as a free person with land and a family of her own seems impossibly far away. That dream hinges on one thing: finding her little sister, Ruth. It’s been years since Ruth was stolen from her. Is she even alive? And if Isabel can find her, how will they make it safely through the war between the Patriots and the British that rages on as dangerously as ever, while bounty hunters try to kidnap them at every turn?

In the American Revolution, one must pick a side in order to survive. But how can you care about a nation’s freedom when the very same nation has kept you in chains?