What was the Quota Act of 1921, and why was it so important?

The Emergency Quota Act of 1921 was passed in the midst of an anti-radical hysteria that swept the United States in the aftermath of World War I. It essentially established quotas that limited all immigration, but, due to the terms of the quota, especially immigration from Southern and Eastern Europe. This was a response to the view among many Americans that Eastern Europeans were not only racially inferior, but brought radical political beliefs like anarchism and communism to the country. Additionally, anti-Semitism and anti-Catholicism were especially strong among some Americans at the time, and this law reflected these trends. It would be followed by a more comprehensive immigration restriction law that actually reduced the numbers of immigrants that could enter the country in 1924. Immigration from some countries was almost totally curtailed by the law. Its historic significance lies in the fact that it represents a longstanding trend of anti-immigrant sentiment, often in response to global events or economic pressures. Often called nativism, discrimination against immigrants has always existed in tension with the idea that the United States is a "nation of immigrants," and the Emergency Quota Act represents a low point in attitudes toward immigrants.