Final answer:
The Johnson-Reed Act of 1924 introduced numerical limits on European immigration and banned immigration from Asia. It aimed to preserve American homogeneity and favor immigrants from western and northern Europe over those from eastern and southern Europe.
Step-by-step explanation:
The 1924 immigration law known as the Johnson-Reed Act was aimed at restricting immigration to the United States in order to preserve American homogeneity. It introduced numerical limits on European immigration based on a quota system that limited annual immigration from any given country to a certain percentage of the residents from that same country as counted in the 1890 census.
The law significantly reduced the share of eligible southern and eastern Europeans, favoring immigrants from western and northern Europe over those from eastern and southern Europe.
In addition to the quota system, the Johnson-Reed Act also banned immigration from Asia, except for people coming from U.S. territories in the Pacific. The law contributed to a shift in the demographics of immigration, opening the door for the formation of Asian and Latin American immigrant communities in the following decades.