While not implicitly racist in itself, eugenics certainly played a role in "racial purity" policies. Although laws banning interracial marriage (i.e., miscegenation) date back to the 18th century in North America, both in French and British colonies, the eugenics movement helped give new impetus to preventing racial mixing in the United States. When Madison Grant published his highly influential The Passing of the Great Race in 1916, he railed against the changing "stock" of immigrants to the U.S. and the decline of the "Nordic" race that had made the country great. As a dedicated eugenicist (who, like Galton never had children of his own), Grant pushed for stronger restrictions on immigration laws and despaired of the prospect of racial mixing which would undermine "Nordic purity". In addition to immigration controls, sterilization of the unfit, and anti-miscegenation laws, Grant also advocated placing inferior races in separate "ghettos" where they could be controlled more thoroughly.
Grant's influence almost certainly played a role in attempts to include an anti-miscegenation clause into the U.S. constitution during that same period (leading to the "one drop of blood rule" for defining race). Between 1913 and 1948, thirty states enacted laws enforcing racial purity while the Immigration Act of 1924 enacted a quota system to exclude Asians and other "inferior" racial groups from immigrating to the U.S. Grant also helped draft racial purity legislation in several states. While Madison Grant was strongly opposed by a coalition of social scientists led by Franz Boas, his work was widely read around the world and helped inspire the growing Nazi movement in Germany (Adolf Hitler personally praised Grant's book as his "bible").
For all his influence, Madison Grant never had great popular appeal and his work was quickly overshadowed by the 1930s. Another prominent name in scientific racism was Charles B. Davenport. As director of the Eugenics Record office at the Cold Spring Harbor Laboratory, Davenport became famous for his reporting on the dire consequences of racial mixing.& Although he admitted that sufficient research had not been done in the area, that didn't stop him from making outrageous conclusions about the mental and physical abnormalities resulting from miscegenation. He concluded that,"hybridized people are a badly put together people and a dissatisfied, restless, ineffective people. One wonders how much of the exceptionally high death-rate in middle life in this country is due to such bodily maladjustments".
The true dean of scientific racism was undoubtedly Theodore Lothrop Stoddard. Born in 1883 of an old New England family, Stoddard graduated from Harvard Law School in 1908 but quickly converted to the
Throughout his books, there was one common theme: that the Nordic race had "clean, virile, genius-bearing blood, streaming down the ages through the unerring action of heredity, which, in anything like a favorable environment, will multiply itself, solve our problems, and sweep us on to higher and nobler destinies." Stoddard viewed World War I as being a disaster for the Nordic race since it was mainly the Nordic soldiers who fought and died while the "inferior Mediterraneans stayed placidly at home". He also warned of the growing Communist threat since, "in every quarter of the globe...the Bolshevik agitators whisper in the ears of discontented colored men their gospel of hatred and revenge. Every nationalist aspiration, every political grievance, every social discrimination, is fuel for Bolshevism's hellish incitement to racial as well as to class war."; Traveling widely, Stoddard took keen interest in foreign policy and wrote about the dangers arising from the geopolitical ambitions of the "coloured" people of Asia, Africa and Latin America.; He also sounded an early warning against the rise of Islam and the dangers of Muslim fanatics. Although a few reviewers had the courage to speak out against Stoddard's books, he was far too popular to be ignored. While hardly the only apostle of scientific racism and eugenics during the 1920s and 1930s, Stoddard was the most well known.
Of course things were changing by then. Despite a greater crackdown on immigration (with the help of eugenics supporters such as Calvin Coolidge and Warren Harding), the actual science on which eugenics/scientific racism was supposedly based became increasingly flimsy. Franz Boas continued his crusade to undermine scientific racism while the mental testing movement began to question whether racial differences in intelligence actually existed. C.C. Brigham, who had written on the superiority of Nordic immigrants on intelligence during the 1920s later reversed himself completely stating that, "comparative studies of various national and racial groups may not be made with existing tests". On the biology front, genetic research completely undermined the concept of race and racist theories in general.
Things were changing on the world front as well. By the late 1930s, Hitler's Germany was showing the entire world what a racist ideology was really capable of doing if taken to extremes. Adolf Hitler and his fellow Nazis hardly needed to depend on Lothrop Stoddard and Madison Grant to support their ideology though. Many of their policies relating to racial theory, antisemitism, and Lebensraum could be traced back to homegrown social scientists such as Alfred Rosenberg and Otto Weininger. While German propaganda films such as Erbkrank were shown by eugenics societies around the world, rumours of what was happening in Germany made even the true believers uncomfortable. Despite reports of forced sterilization, ghettoes, and persecution, the full extent of the Nazi eugenics program didn't become apparent until after the end of World War II.