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After the New World was discovered by Europeans, people from all over morthwestern Europe sailed across the Atlantic to settle North America.
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That was the biggest movement of poeple in the history.
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Between 1845.1848 come over one million people to America because the farmland was cheap.
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After the discovery of gold in California in 1849
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In 1920s was America build up of more than 100 diffrent ethnic groups.