【Abstract】 During most of the 20th century the U.S.government carried out the free immigration policy.Most Americans understood that it was necessary to fill up the country and welcome most of the foreigners who came to settle.However,that welcome was not unalloyed,and three phases of anti\|immigrant activity can be ascertained.The first phase was the anti\|Catholic movement flourishing from the late 1830s to the mid\|1850s.In some respects,it never completely died out.The second phase was anti\|Asian movements which were directed against Chinese,Japanese and Filipinos respectively from the late 19th century to 1930s.The third phase was a movement for general restrictions on immigration beginning in the mid\|1880s,which finally triumphed in the National Origins Act of 1924.The National Origins System was based on racism,especially the sense of Anglo\|Saxon superiority,which dominated American immigration policy for the next forty years.更多还原