What are three acquisitions that greatly expanded the territory of america before the civil war?

How did the mountains on the oregon trail influence the timing of pioneers’ travels? a.) the pioneers wanted to avoid times when there was snow in the mountains. the pioneers wanted to spend as much time as possible enjoying the mountain scenery. b.) the pioneers crossed the mountains in late fall when the trees were bare and the views were good. c.) the pioneers were rugged people who were not impacted by the terrain they crossed at any time.