The Justice League – This Day In Comics
The Brave and the Bold #28 – Starro the Conqueror!
The Justice League first appeared in The Brave and the Bold #28 (December 29, 1959).
The Justice League of America first appear with Wonder Woman, The Flash (Barry Allen), Aquaman, Green Lantern (Hal Jordan), and the Martian Manhunter teaming to spare the denizens of Happy Harbor, Rhode Island, from the mental thrall of Starro the Conqueror.