What law established a quota system for immigrants?

The Immigration Act of 1924, also known as the Johnson-Reed Act, established a quota system for immigrants entering the United States. This law set limits on the number of immigrants allowed from each country, favoring northern and western European countries while severely restricting immigration from southern and eastern Europe, as well as Asia. The quotas were based on the national origins of the U.S. population, effectively aiming to preserve the existing demographic composition of the country.