The Justice League of America was formed when an alien incursion from the planet Appelax forced seven of the World’s Greatest Super Heroes to come together and defeat them. After Superman, Batman, Wonder Woman, Flash, Green Lantern, Aquaman, and the Martian Manhunter came together to repel the invasion, they decided to regularly band together to tackle crimes too large for one hero to handle alone. They set up their headquarters in a mountain in Happy Harbor, Rhode Island, and although Superman and Batman were only part time members in those early years, they successfully saved the world from the likes of alien despots Despero and Kanjar-Ro, the sorcerer Felix Faust, and Starro, the Conqueror.
In time, the League inducted more heroes, like the Green Arrow, the Atom, Hawkman, and Black Canary. During these early years, the JLA made contact with the parallel world of Earth-2, where their predecessors the Justice Society of America had fought in the days of World War II. This began an annual tradition, where the JLA and the JSA would cross dimensions and share an adventure together. One of those adventures was joining forces to battle the Crime Syndicate of Earth-3, who were all evil doppelgangers of the League, and who would return to menace the team time and again. It was during the end of the Silver Age that the team’s mascot, teenager Snapper Carr, betrayed the location of the League’s home base to the Joker. Around this time, Wonder Woman lost her powers and left the League. These were the first two large blows to the team’s morale.
The Bronze Age
After the breach of their original home by the Joker, the League found that they needed a better, more secure base of operations, and they built a sophisticated orbiting satellite headquarters, some 22,300 miles above the Earth. During this time, the JLA grew in power, as they added new members like the Elongated Man, the android Red Tornado, Hawkgirl, the sorceress Zatanna, and Firestorm. Wonder Woman returned to the team during this time, and the Martian Manhunter left for a long sabbatical.
Personal crises drew various veteran members away as the League grew larger. Batman left to found his own team, the Outsiders, and other members kept getting drawn away from the League by personal problems. With several of their “big guns” gone, the team was vulnerable to a Martian invasion that left the JLA satellite in pieces. With their high tech HQ gone, Aquaman disbanded the League, and reformed it with only members who would dedicate themselves to the team full time. Superman, Wonder Woman, Flash, Hawkman and Hawkgirl, Red Tornado, Firestorm and Green Lantern all declined to commit to the team full time. Only Aquaman, Zatanna, the Elongated Man, and the newly returned Martian Manhunter remained.
This new full time JLA set up shop in a bunker in Detroit, and were soon joined by a group of young heroes who wanted to join the team. Vibe and Gypsy were young metahuman street kids, and they were soon joined by Vixen and Steel. Despite their best intentions, this “Justice League Detroit” simply couldn’t cut it, and never lived up to the potential of the team’s legacy. After a brief couple of years, two members of the group, Vibe and Steel, were brutally murdered by the villainous Professor Ivo – the first Leaguers to die in the line of duty. In light of the tragedy, the Martian Manhunter disbanded the JLA, seemingly for good.
Following the events of 1985-1986's CRISIS ON INFINITE EARTHS, Darkseid’s tried and failed to get the people of Earth to turn against their heroes. The League then reformed again, with Batman rejoining the team, along with Black Canary and the Martian Manhunter. New members were added when Blue Beetle, Dr. Fate, Mr. Miracle, Shazam, Green Lantern Guy Gardner and Dr. Light joined the group. Under the manipulations of the mysterious billionaire Maxwell Lord, the team added new members, like Booster Gold, Captain Atom, and the Soviet Rocket Red, along with Fire and Ice. Lord’s goal was to move past the idea of the Justice League of America, and get a United Nations charter and become the Justice League International. The new JLI opened up embassies all over the world, and permanent team was housed in their Paris location, later dubbed the Justice League Europe. New recruits for the European League were heroes like Power Girl, Animal Man, Metamorpho, and the Wally West incarnation of the Flash.
During the next few years, the League kept expanding and contracting – prominent members would leave, while new heroes would join up. New branches of the League like the Justice League Task Force and Extreme Justice were established, and would then quickly dissolve. Instead of the World’s Greatest Super Heroes, the League had become famous for being the home of lesser known costumed adventurers, many who weren’t exactly worthy of the team founded by the likes of Superman, Batman and Wonder Woman.
Things changed when the alien Hyperclan came to Earth, promising to be the heroes who would truly save the world in a way the League never had. But these aliens were, in fact, white Martians in disguise, and plotted to take the Earth for the own. Superman, Batman, Wonder Woman, Aquaman, Martian Manhunter, and the inheritors of the mantles of the Flash and Green Lantern came together to rid the world of the alien invaders, and to restore the Justice League to greatness once more.
The new powerhouse League built a Watchtower on the moon, from which they monitored all activity on Earth. This iteration of the team was perhaps its most powerful, as they took on the threats like the rogue angel Asmodel, the Injustice League, Darkseid, and the apocalyptic anti-sun known as Mageddon. The roster expanded to include heroes like Big Barda, Orion of the New Gods, Plastic Man, Huntress, Oracle, and Steel. The Justice League now resembled the Gods of ancient Greece, and the moon based Watchtower was their Mount Olympus.
This “Big Guns” JLA stayed mostly intact until the events of the Infinite Crisis, after which Superman, Batman, and Wonder Woman vanished for a year. When they returned one year later, they built a new Justice League of America, one which had a new headquarters on Earth called the Hall of Justice, along with a new satellite Watchtower. New recruits during this era were former Green Arrow sidekick Arsenal, along with Black Lightning. Former Teen Titans Cyborg, Starfire, Donna Troy and Dick Grayson, now using the title of Batman, joined the team during this time as well.
Following the events of 2011's FLASHPOINT, the history of the DC Universe was reimagined, and the entire history of the Justice League was erased. In this New 52 timeline, the League was founded by Superman, Batman, Wonder Woman, Green Lantern Hal Jordan, Flash Barry Allen, Aquaman, and Cyborg. Martian Manhunter was not a founder in this new history. The team was able to repel an invasion from Darkseid, and this roster of seven did not add any new heroes to the team for their first five years in existence. Eventually, they would add Firestorm, Element Woman, and a new female Atom to the League. But this new Atom was a spy, studying the team for the evil Crime Syndicate of Earth-3. This precipitated an invasion of the Earth by the Syndicate, an invasion they ultimately repelled.
Other teams with the name Justice League formed in response to the main League, like Justice League International, a United Nations sponsored team, and the Justice League Dark, a group of heroes who investigate mystical threats. The United States government even formed their own League, which they created in the event of the actual Justice League ever going rogue.