The final phase of the eugenics movement occurred after 1930 when the movement rapidly disintegrated. Three events hastened the demise of the eugenics movement in the United States. First, the Depression of the 1930's discredited Social Darwinism, along with the "business elite" who professed such conservative viewpoints. Americans began to realize that failure no longer hinged on individual weakness or lack of ability. Both the biologically "fit" and the "unfit" shared in the misfortunes of the Depression. Secondly, more sophisticated research during the 1930's discredited much of the scientific premises of Galtonian eugenics. Scientists, like Irving A. Folling and Herbert J. Muller, discovered metabolic causes for certain mental retardation and genetic mutations caused by radiation that refuted the hereditary degeneracy of Dugdale's Jukes and Goddard's Kallikaks. And finally, the rise of Hitler-style eugenics with its grotesque and barbaric methods for eliminating "inferiors" horrified Americans. Realization of the full implications of eugenics abruptly halted racial reforms in the United States.
Today, the underlying motives for the eugenics movement during the first two decades of the twentieth century are not dead. Racist eugenics has remained on the fringes of American social thought since 1945, periodically re-emerging into the mainstream in varying degrees and forms. Americans continue to question the intellectual and moral capabilities of numerous non-white groups. Americans have consistently forced its "superior" social institutions - - democracy, capitalism and Christianity - - upon ethnic and racial groups throughout the world, and have subscribed to racial prejudices that maintain a belief in the innate inferiority of "colored peoples".
Today, birth control remains a method of controlling ~ "undesirable" African and Asian populations, along with reducing the propagation of welfare recipients at home. Americans continue to express concern of the "new immigrants" - - the Vietnamese, Filipino, Latin American and Arab - - who seem to fail in assimilating to American ideals, values and culture. Today, as in the past, certain Americans voice fears of a declining Anglo-American birthrate and a burgeoning Black population in America's cities. Today, institutionalization and sterilization of "defectives" remains the answer of a society that desires to segregate the "unfit" from mainstream America. Thus, a movement, which had its heyday from 1905 to 1930, has the makings of revitalization during the 1970's and 1980's.
UPDATE: In the 21st century, Americans are seeing a rebirth of neo-eugenics as we debate the ethics of cloning and genetic manipulation in an effort to combat disease and illness. The temptation remains for modern day eugenicists to weed out perceived "undesirable" human traits. Who will become the "breeders" and who will become the "undesirables?"