The correct answer is - the 1850's.
The Chinese immigration towards the United States of America significantly increased during the 1850's. This was due to the loosened up immigration policy by the United States in this period, so lot of Chinese poor people saw an opportunity for better life, and they rushed into the United States. Before this decade, the Chinese were discriminated against in the immigration policy of the United States as only a very small, limited number of Chinese people were allowed to migrate into the country.
