Congress established the U.S. Immigration Commission under the leadership of Vermont Senator William Dillingham to analyze the impact of increased immigration to the U.S.
For three years, the commission members conducted interviews and analyzed data, equipped with the tools of eugenics (see also: Eugenics Movement, 1916), a philosophy and set of principles that promote selective reproduction and reproductive control with a goal of genetic improvement. In 1911 the Commission issued their conclusions that immigration “from southern and eastern Europe posed a serious threat to American society and culture, and therefore should be reduced.” Their findings included statements such as, “Bohemians are the most nearly like Western Europeans of all the Slavs. Their weight of brain is said to be greater than that of any other people in Europe.”
While the Commission’s methodology is considered reprehensible by today’s standards, their work was praised at the time. Their reports provided the basis for the imposition of restrictive immigration quota laws in the 1920s (see also: The Quota Act, 1921-1924) and contributed pseudo-scientific evidence to a growing discriminatory fervor against immigrants.