Justice Society of America, Vol. 3 by Geoff Johns

Superman versus aliens? That was Earth-1. Continuity had been invented by this point, so the explanation was, 'All those JSA stories took place on Earth-2, which has its own version of Superman, and everything from, uh, circa-1955 on is from Earth-1, which has the Justice League of America. Over a decade later, superheroes were on the rise again and The Flash (the Silver Age Flash, a totally different guy than the one in World War II) discovered another Earth inhabited by the older Golden Age characters. The comic was canceled with issue #57 (February-March, 1951) at the end of The Golden Age of Comic Books, with All-Star Western continuing the numbering. The team had a roster that changed from time to time, with characters leaving the team and others replacing them, until finally the lineup stabilized for the last two years of the book's run. As the Trope Maker for Super Team, the Justice Society was mostly reserved for lesser-used characters and any character who got his own series would have minimal appearances, so Flash and Green Lantern left when they got solo comics, Superman and Batman rarely appeared note They had their own books, and the publisher believed that including them would cannibalize sales, and Wonder Woman was the JSA's secretary and didn't go on missions until late in the Golden Age All-Star run. Thus was born the world's first superhero team. However in the third issue (Winter, 1940), writer Gardner Fox introduced the Justice Society of America, teaming up the characters.

The comic book All-Star Comics, in 1940, was introduced as a standard anthology title featuring characters from other anthologies.

They were being read by Depression-era kids, who weren't going to write to the editor and complain about how the current issue of The Flash was at odds with a story written three years before. All those comics on the stands? They didn't intersect with one another. Once upon a time, comics had no such thing as continuity. 'During the days of World War II, a group of costumed mystery men gathered together to form the first and greatest super-team of all time.'

Justice Society of America, Vol. 3 by Geoff Johns