The beginning (as well as the end) of the Silver Age is cause for debate, but it is generally agreed that the period began with DC Comics' Showcase #4 in 1956, which introduced the modern version of the Flash. Under editor Julius Schwartz, the Flash was the first of many old characters revised as streamlined, science fiction-influenced models. Others included Green Lantern, the Atom and Hawkman. DC also introduced The Justice League of America, an all-star group consisting of its most popular characters.
The success of these series meant DC had found a viable format that could make for successful properties under Comics Code Authority restrictions. This helped breathe new life into the medium and sales began to recover.
The period also saw the rise of Marvel Comics, under the guidance of writer-editor Stan Lee and artists/cowriters Jack Kirby and Steve Ditko, who introduced more sophisticated characterization and dynamic plotting into superhero comics. The most popular and influential Marvel character of this period was Spider-Man. Other significant and long-lasting Marvel heroes introduced during the Silver Age include The Fantastic Four, The Incredible Hulk, Iron Man, Thor, Daredevil, The X-Men, and Marvel's own all-star group, The Avengers. After an initial period of hesitance, DC began to adopt some of Marvel's creative approaches.
The resurgence of superheroes proved so influential that publishing houses not known for such characters — including Archie Comics, Charlton Comics and Dell Comics — attempted their own superheroes, but met with limited critical and popular success. Tower Comics was an exception with the well-received if short-lived T.H.U.N.D.E.R. Agents series by Wally Wood.
In addition, new artists, many of whom grew up with comics as well as being formally trained, began to expand the mainstream medium into new art styles. Major examples include Neal Adams who introduced naturalism with his illustrative style, and Jim Steranko who introduced op art, touches of Surrealism, and graphic design elements.
The period hit its commercial peak in 1966-1968 with the popularity of the Batman TV series, which both heightened interest in comics and damaged their public image as a legitimate artistic medium.
Underground comics got their start during the 1960s portion of the Silver Age. However, because the artistic content, goals and marketing of these comic books were so different from the mainstream companies, it is generally considered a separate movement in the medium.