In the mid-1910s, Popenoe became interested in human breeding and edited the Journal of Heredity from 1913 to 1917, with a special attention to eugenics and social hygiene.
An elementary knowledge of the history of Africa, or the more recent and much-quoted example of Haiti, is sufficient to prove that the Negro's own social heritage is at a level far below that of the whites among whom he is living in the United States....
Under the War Department Commission on Training Camp Activities, he was charged with rooting out liquor and prostitution in an effort to reduce the high incidence of venereal disease in US troops.
That would culminate in a number of works, most prominently their joint-authored Sterilization for Human Betterment: A Summary of Results of 6,000 Operations in California, 1909-1929 in 1929.
In the 1930s, he served as a member of the American Eugenics Society's board of directors, along with Charles B. Davenport, Henry H. Goddard, Madison Grant, Harry H. Laughlin, and Gosney, among others.
[5] Leading up to that vote, Occidental Professor Peter Dreier wrote an opinion article in March 2019 about the college's historical role in eugenics and racism, and 86 percent of the college's faculty then signed a statement urging the board to revoke the degree granted to Popenoe 90 years earlier.
[6] Along with his advocacy of sterilization programs, Popenoe was also interested in using the principles of German and Austrian marriage consultation services for eugenic purposes.
[7] One of the greatest dangers in the use of sterilization is that overzealous persons who have not thought through the subject will look at it as a cure-all, and apply it to all sorts of ends for which it is not adapted.
[8]For a while, Popenoe's two major interests, eugenics and marriage counseling, ran in parallel, and he published extensively on both topics.
In that vein, he appeared on the Art Linkletter television show for over a decade, and he regularly gave lectures and wrote mainstream articles for the general public.
[7] At the peak of his career, he co-founded and edited Ladies' Home Journal's most popular column of all time, "Can This Marriage Be Saved?"
[10] As Popenoe maintained his traditional values (chastity before marriage), changes in popular culture such as feminism and sexual revolution challenged his approach.
In the US society of the third millennium, the approach Popenoe developed to marriage counseling, educational and directive rather than medical or psychological, is becoming fashionable again.
In 2002, the American Heritage Center of the University of Wyoming reported the collection Paul Bowman Popenoe Papers, 1874–1991, consisting of 85 cubic feet of material.