Even the United States Supreme Court endorsed aspects of eugenics. In its infamous 1927 decision, Supreme Court Justice Oliver Wendell Holmes wrote, "It is better for all the world, if instead of waiting to execute degenerate offspring for crime, or to let them starve for their imbecility, society can prevent those who are manifestly unfit from continuing their kind…. Three generations of imbeciles are enough." This decision opened the floodgates for thousands to be coercively sterilized or otherwise persecuted as subhuman. Years later, the Nazis at the Nuremberg trials quoted Holmes's words in their own defense.

Only after eugenics became entrenched in the United States was the campaign transplanted into Germany, in no small measure through the efforts of California eugenicists, who published booklets idealizing sterilization and circulated them to German officials and scientists.

Hitler studied American eugenics laws. He tried to legitimize his anti-Semitism by medicalizing it, and wrapping it in the more palatable pseudoscientific facade of eugenics. Hitler was able to recruit more followers among reasonable Germans by claiming that science was on his side. While Hitler's race hatred sprung from his own mind, the intellectual outlines of the eugenics Hitler adopted in 1924 were made in America.

Smith and I found that, of the nearly 1,800 articles published across the four editions of the encyclopedia, only 13 addressed racism in a substantive way.