Then beginning in the mid-1830s missionaries and settlers began to arrive in the region Also the majority of the Native Americans in many areas were killed off by diseases introduced by Euro-Americans, including up to 70 percent in the Willamette Valley and Lower Columbia valley by 1830. Mass migration began in 1842 when a wagon train of around 100 wagons came overland along the Oregon Trail.
From the mid-1830s, missionaries and settlers started arriving in the region. Additionally, many Native Americans were affected by diseases brought by Euro-Americans, with up to 70 percent dying in certain areas by 1830. Mass migration began in 1842 when a wagon train of approximately 100 wagons traveled overland along the Oregon Trail.