It is 1848 when Joshua McCullough and his family leave their home in St. Joseph, Missouri, and set off for Oregon on a wagon train. During their seven-month-long journey, many of the other families on the trail suffer devastating losses, but Joshua's is spared. However, Joshua must conquer his fear of water during the many river crossings the wagon train must make. During one dramatic crossing, Joshua heroically dives into a rushing river to save his younger sister Becky. The battered wagon train reaches Oregon after traveling over two thousand miles.