The opening decades of the 20th century saw increasing agitation over the growing number of immigrants coming to American shores. Initial resistance was directed against the Japanese, particularly in California, where many feared that the labor market was being flooded. Crises developed during the administrations of Theodore Roosevelt and Woodrow Wilson, and developed to the point that war against Japan was loosely discussed as a recourse.
Later, during World War I, critics of immigration turned their attentions to newcomers from southern and eastern Europe. Their languages, customs and religion differed sharply from those of the earlier immigrants from Northern Europe and the British Isles. Efforts were made to slow the flood by imposing a literacy test on those wishing to enter the U.S. Wilson twice vetoed these measures, but Congress overrode his veto, in 1917.
Congress also acted to deny entry to suspected anarchists, an action prompted by the Bolshevik Revolution in Russia and its proclaimed goal of world revolution. Suspicions about foreigners spilled over in the Red Scare of 1919-20, when thousands were arrested for real or imagined revolutionary activity.
Immigration reform, sometimes known as the Emergency Immigration Act of 1921, was prompted by the news that in the preceding 12 months more than 800,000 foreigners had entered the United States. Congress responded by establishing the first quota system that provided for the following:
Immigration from a specific nation was limited to three percent of that nations population living in the United States, as reported in the 1910 Federal Census.
An overall maximum annual quota of 357,000 was imposed.
This law was intended to be only a stop-gap measure until the immigration matter could be more closely studied and a new law crafted. Further immigration tightening followed in 1924.