A term describing a period beginning in the mid-1950s when superheroes made a successful comeback in comic books. Nearly everyone agrees that the Silver Age began with the publication of DC Comics' Showcase #4, which introduced the new and improved Flash. Other early milestones included the new and improved Green Lantern, the first appearance of the Challengers of the Unknown, the introduction of the Justice League of America, and the first appearance of the Fantastic Four. According to the Overstreet Comic Book Price Guide, the Silver Age ended in 1969.