What were the reasons for the late nineteenth century boom on migration to the West from the eastern United States and Europe?

Okay, so, just from the top of my head, I think that it is because of the growing belief of "Manifest Destiny" in the nineteenth century. I'm not sure if this is the actual right answer for your question, but I do know that Manifest Destiny was in the nineteenth century and was the widely held belief in the USA that American settlers were destined to expand through out the continent. And I think both the USA and Europe wanted to expand, it was kind of a copetition/conflict they had. This was actually how Canada and Alaska came to be I believe. This was a simple explanation btw. cx