The Immigration Act of 1924, or Johnson-Reed Act, including the National Origins Act, Asian Exclusion Act, (43 Statutes-at-Large 153) was a United States federal law that limited the number of immigrants who could be admitted from any country to 2% of the number of people from that country who were already living in the United States in 1890, according to the Census of 1890. It excluded immigration of Asians. It superseded the 1921 Emergency Quota Act. The law was aimed at further restricting the Southern and Eastern Europeans who were immigrating in large numbers starting in the 1890s, as well as prohibiting the immigration of East Asians and Asian Indians.
Congressman Albert Johnson and Senator David Reed were the two main architects. In the wake of intense lobbying, the Act passed with strong congressional support.<1> There were six dissenting votes in the Senate and a handful of opponents in the House, the most vigorous of whom was freshman Brooklyn Representative Emanuel Celler. Over the succeeding four decades, Celler made the repeal of the Act into a personal crusade. Some of the law's strongest supporters were influenced by Madison Grant and his 1916 book, The Passing of the Great Race. Grant was a eugenicist and an advocate of the racial hygiene theory. His data purported to show the superiority of the founding Northern European races. But most proponents of the law were rather concerned with upholding an ethnic status quo and avoiding competition with foreign workers
http://en.wikipedia.org/wiki/Immigration_Act_of_1924