Help with DBQ essay (immigration) How do i begin introduction?

the historical content is "united states policy has change over time to reflect the needs ant attitude of American society".
Task: Discuss immigration POLICIES OR ACTION taken by the united stated gov. that affected the immigration of people to the U.S
>Show how these policies or actions reflect the needs and attitude of American society at that time.
(need to include Old/new imm. ; push/pull factors ;ellies island ; anti imm ; know nothing party ;

Answer:
High cost of cheap labor. Thats the name. Heh.
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