Before the war, when about a million immigrants arrived each year, some Americans warned that unassimilable foreigners were smothering the nation. War against Germany and its allies expanded nativist and antiradical sentiment. After the war, large-scale immigration resumed (another 800,000 immigrants arrived in 1921) at a moment when industrialists no longer needed new factory laborers. Returning veterans, as well as African American and Mexican migration, had relieved labor shortages. Moreover, union leaders feared that millions of poor immigrants would undercut their efforts to organize American workers. Rural America’s God-fearing Protestants were particularly alarmed that most of the immigrants were Catholic or Jewish. In 1921, Congress responded by severely restricting immigration.

In 1924, Congress very nearly slammed the door shut. The Johnson-Reed Act limited the number of immigrants to no more than 161,000 a year and established quotas for each European nation. The act revealed the fear and bigotry that fueled anti-immigration legislation. While it cut immigration by more than 80 percent, it squeezed some nationalities far more than others. Backers of Johnson-Reed, who declared that America had become the “garbage can and the dumping ground of the world,” manipulated quotas to ensure entry only to “good” immigrants from western Europe. The law effectively reversed the trend toward immigration from southern and eastern Europe, which by 1914 had amounted to 75 percent of the yearly total.

The 1924 law reaffirmed the 1880s legislation barring Chinese immigrants and added Japanese and other Asians to the list of the excluded. But it left open immigration from the Western Hemisphere because farmers in the Southwest demanded continued access to cheap agricultural labor. During the 1920s, some half a million Mexicans crossed the border. In addition, Congress in 1924 passed the Indian Citizenship Act, which extended suffrage and citizenship to all American Indians.

Antiforeign hysteria climaxed in the trial of two anarchist immigrants from Italy, Nicola Sacco and Bartolomeo Vanzetti. Arrested in 1920 for robbery and murder in South Braintree, Massachusetts, the men were sentenced to death by a judge who openly referred to them as “anarchist bastards.” In response to doubts about the fairness of the verdict, a blue-ribbon review committee found the trial judge guilty of a “grave breach of official decorum” but refused to recommend a motion for retrial. When Massachusetts executed Sacco and Vanzetti on August 23, 1927, fifty thousand American mourners followed the caskets, convinced that the men had died because they were immigrants and radicals, not because they were murderers.