First published in March-April of 1956, the title ran uninterrupted until issue #93 in September of 1970. The series picked back up after a seven year absence with issue #94 in September 1977 and continued until September 1978 with issue #104.

The series, sometimes referred to as "Showcase Presents" featured as a testing ground for new characters. And featured the first appearance of many Silver-Age characters.

First appearances:

#4: Flash (Barry Allen)
#6: Challengers of the Unknown
#15: Rick Starr, Space Ranger
#17: Adam Strange
#20: Rip Hunter
#22: Green Lantern (Hal Jordan)
#27: Sea Devils
#34: Atom (Ray Palmer)
#37: Metal Men
#41: Tommy Tomorrow
#62: Inferior Five
#66: B'wana Beast
#68: Maniaks
#73: The Creeper
#74: Anthro
#75: Hawk and Dove
#76: Bat Lash
#77: Angel and the Ape
#78: Jonny Double
#79: Dolphin
#82: Nightmaster
#85: Firehair
#90: Manhunter 2070
#94: The new Doom Patrol