This was actually held in 1843 when the first large-scale migration to oregon country take place, and therefore, there was large amoint, just about thousands of pioneer's ready to take on action. They made sure that this scale would decrease.
As with most locations for settlements in any civilization the key factor is settlements were located in the lowlands where the land was fertile and could be farmed. Geography is very important when a site is picked for settlement. The site must be able to support human activity.
