The Immigration Act of 1924, also known as the Asian Exclusion Act, was a United States federal law which was enacted on 26 May 1924, preventing immigration from Asia, setting quotas on the number of immigrants from Europe, and providing funding and an enforcement mechanism to carry out the longstanding ban on other immigrants. It effectively banned all Asian immigration and set an immigration quota of 165,000 for countries outside the Western Hemisphere, reducing immigration by 80% and setting 2% quotas on the source countries of immigrants; the law especially affected Italians and Jews.
The law was passed as the result of the concurrent Eugenics crusade in the USA, with prominent eugenicist Harry H. Laughlin convincing Congressman Albert Johnson that most immigrants had "undesirable traits" such as "feeble-mindedness", "criminality", "immorality", and other traits, and that the arrival of thousands of foreign-speaking peasants would endanger the "Old Stock" (white Anglo-Saxon Protestants of colonial heritage) elite of America. The laws were not altered even during the start of Nazi Germany's persecution of Jews during the 1930s, and they would not be repealed until the passage of the Immigration and Nationality Act of 1965.