A costumed adventurer, also known as a masked vigilante or a "superhero", is any character who dresses in elaborate clothing to battle crime. Practitioners might also employ specially-designed and custom-built weapons to aid themselves, as in the case of Nite Owl II, who designed much of this type of weaponry on his own. Those who engage in this type of crime fighting possess a general belief that existing law enforcement either requires assistance, or is somehow inadequate, in investigating, locating and/or apprehending criminals. The presence of costumed adventurers is often considered controversial since those who have chosen this way of life do so outside the purview of due process of law, thereby making their actions illegal, part of the larger concept of vigilantism, which is a key concept and theme in Watchmen.
The first costumed adventurer to be featured in the news was Hooded Justice (although it is mentioned that Silk Spectre was featured in an interview earlier). These first adventurers were looked upon favorably, and the Minutemen were often seen as heroes to the cause of criminal justice. Their actual identities were also closely guarded secrets. While the adventurers where inspired and motivated by the fictional pulp heroes of the '40s, their existence brought a decline to this genre of literature, and comic books turned to pirate-themed stories.
Throughout World War II, Nazi Germany employed masked agents like Screaming Skull and Captain Axis. The adventurers confronted other persons who assumed masked identities as villains, like King Mob and Screaming Skull. When they Minutemen were dissolved, Captain Metropolis attempted to resurrect vigilantism with the Crimebusters.
During that era however, costumed adventuring began to lose much of its appeal since American society began to shift radically, especially during the 1960s when social unrest became much more prominent. The year 1977 saw a national strike by police, who felt their jobs were at stake because of vigilantism. Later that same year, the Keene Act was passed, making costumed adventuring illegal, unless participants were willing to enter government service, as did the Comedian and Dr. Manhattan who had cooperated earlier in Vietnam. Dan Dreiberg and Laurie Juspeczyk both retired their costumed personae but did not take the route of Ozymandias, who had chosen to make his identity public (two years prior to Keene's passage) and built a multi-billion corporation from his superhero image.