The popularity of superhero comic books declined following World War II, while comic book sales continued to increase as other genres proliferated, such as romance, westerns, crime, horror, and humour. Following a sales peak in the early 1950s, the content of comic books (particularly crime and horror) was subjected to scrutiny from parent groups and government agencies, which culminated in Senate hearings that led to the establishment of the Comics Code Authority self-censoring body. The Code has been blamed for stunting the growth of American comics and maintaining its low status in American society for much of the remainder of the century. Superheroes re-established themselves as the most prominent comic book genre by the early 1960s. Underground comix challenged the Code and readers with adult, countercultural content in the late 1960s and early 1970s. The underground gave birth to the alternative comics movement in the 1980s and its mature, often experimental content in non-superhero genres.

Which genre of comic books had parents concerned?