What caused nativism and quota laws 1920s?

Nativism, term used to refer the policy of promoting the interests of native inhabitants against those of immigrants, and the called quota laws in 1920s were caused mostly by the uncertainty generated over national security during World War I, which made it possible for Congress to pass the first widely restrictive immigration law in 1917 that included several important provisions that paved the way for the 1924 Act.

The 1917 Act implemented a literacy test that required immigrants over 16 years old to demonstrate basic reading comprehension in any language. However, the literacy test described above was considered not enough to prevent most potential immigrants from entering, therefore members of Congress sought a new way to restrict immigration in the 1920s. In this sense, immigration expert and Republican Senator William P. Dillingham introduced a measure to create immigration quotas. He set the percent of the total population of the foreign-born of each nationality in the United States basing on in the 1910 census.

In this way, it was limited the number of immigrants allowed to entry into the United States through a national origins quota. This put the total number of visas available each year to new immigrants at 350,000, excluding completely immigrants from Asia.