The 1965 Immigration Act abolished the national-origin quota system that had been executed in the United States since the Immigration Act of 1924. From 1924 to 1965, the U.S. government limited the number of immigrants who could be admitted from any country to 2% of the number of people from that country who were already living in the U.S. in 1890. The Immigration Act of 1924 prohibited immigration from Asia, especially for East Asians and Asian Indians; it also restricted the numbers of immigrants from southern and eastern Europe. As a result, immigrants during this period were mainly Europeans from countries such as Ireland, England, and Germany.

Lee, E. (2006). A nation of immigrants and a gatekeeping nation: American immigration law and policy. In R. Ueda (Ed.), A companion to American immigration (pp. 5-35). Malden, MA: Blackwell.