The scripts for the first stories are often credited to Dick and Dave Wood, two brothers who also wrote other Kirby-illustrated material, such as the "Sky Masters of the Space Force" comic strip; but others have claimed that Kirby created the Challengers himself or together with former partner Joe Simon. The stories had weird menaces, fistfights, wild vehicles and gadgets, spectacular terrain, daring escapes, and a sense of humor.
The group debuted in Showcase #6 (Feb. 1957). The inspiration for the Challengers' adventures were old serials, war movies, and drive-in science fiction. Superhero comics had mostly vanished from about 1949 to the mid-1950s revival of the Flash, seen as marking the return of the superheroes to popularity, had occurred only four months earlier, in Showcase #4.
The most noted influence of this creation was Kirby's next major continuing series, The Fantastic Four, which was essentially the Challengers as a superhero family, complete with a similar origin. Both groups were quartets who resolved to band together after a crash landing; but the Challengers lacked the strong characterizations and much of the humor that distinguished the Fantastic Four. In Challengers of the Unknown #3, Rocky was shot into space and returned with multiple superpowers including invisibility, flame throwing, freeze-ray throwing, giant-growth, super-speed and super-strength.
The series continued in Showcase for three more appearances (#7, 11, 12) then moved to its own title, considered among Kirby's most notable in that period. After 12 issues total, Kirby moved on, and the title continued through issue #75 (Aug.-Sept. 1970, followed by intermittent reprint and revival issues from 1973-78). The Challengers were canceled with issue #77 in 1971. In 1973, three reprint issues were put out (#78-80).