Actually Darwin himself was writing about natural selection, human breeding, and races in 1871 [1]
> With savages, the weak in body or mind are soon eliminated; and those that survive commonly exhibit a vigorous state of health. We civilised men, on the other hand, do our utmost to check the process of elimination; we build asylums for the imbecile, the maimed, and the sick; we institute poor-laws; and our medical men exert their utmost skill to save the life of every one to the last moment. There is reason to believe that vaccination has preserved thousands, who from a weak constitution would formerly have succumbed to small-pox. Thus the weak members of civilised societies propagate their kind. No one who has attended to the breeding of domestic animals will doubt that this must be highly injurious to the race of man.
https://en.wikipedia.org/wiki/The_Descent_of_Man,_and_Select...
Galton, the "Father of Eugenics" was already proposing eugenics related things in the 1860's, and by the 1900-1910 it was getting into full swing in the US.