Around 1905 he relocated with his family to Southern California, eager to escape the "wild west" environment still present in Arizona while raising two daughters.

By the 1920s he had built up a considerable fortune, owned one of the largest lemon groves in the state, and served as the director of numerous banks, trusts companies, and corporations.

[citation needed] In 1933 officials in Nazi Germany specifically referred to Gosney and Popenoe's book in the creation of their own sterilization legislation that year.

According to a U.S. health official at the time, who had just returned from a trip to Germany, "the leaders in the German sterilization movement state repeatedly that their legislation was formulated only after careful study of the California experiment."

(quoted in Kühl 1994, p. 42-43) Gosney and Popenoe believed the population of mentally ill in the United States could be reduced by half in "three or four generations."

The Sacramento philanthropist/eugenicist Charles Goethe wrote to Gosney in a 1934 letter: A follow-up study, Twenty-eight Years of Sterilization in California, was published by the pair in 1938.

As Gosney put it, the Foundation would work for: The initial board of trustees was Gosney, Henry M. Robinson (a Los Angeles banker); George Dock (a Pasadena physician); Justin Miller (dean of the college of law at the University of Southern California); Otis Castle (a Los Angeles attorney); Joe G. Crick (a Pasadena horticulturist); Goethe, and Popenoe.

It also underwrote a column in the Los Angeles Times on "social eugenics", and financed a radio program and hundreds of popular lectures around the country to educate people about the subject.