What were some important events in the mid 1800s that cause many Europeans to immigrate over to America?

exactly the title. I am doing an immigrant report and I need to find out why an ancestor of mine left Switzerland for America. Besides the knowledge that america had more oppurtunities, is there any major event (war, famine, health reasons, ect.) why they might of left to go to America? ANY info is helpful. THANK... show more exactly the title. I am doing an immigrant report and I need to find out why an ancestor of mine left Switzerland for America. Besides the knowledge that america had more oppurtunities, is there any major event (war, famine, health reasons, ect.) why they might of left to go to America? ANY info is helpful.
THANK YOU :)
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