Lost in the Past — Jeanie Johnson

Intent on escaping to the future, in order to leave the new revolution behind, Tabitha, instead, finds herself on the Oregon Trail in 1845. Zack, the wagon train scout takes her under his wing, but since she doesn't know where the portal is, she wonders if she will be forced to live a life in the past, making history before she was ever born, and never find her way back again?