The legacy of the Know-Nothings lived beyond its life as an organization. The seeds of bigotry, fear and hatred bore fruit again in the years after the Civil War.[…] The First World War led to another outbreak of nativism. A new group, adopting the program of the Know-Nothings and the name of the Ku Klux Klan, came into being, denouncing everything its members disliked—Negroes, Catholics, Jews, evolutionists, religious liberals, internationalists, pacifists—in the name of true Americanism and of “Nordic superiority.”
Source: wiktionary