Over a decade ago, Earth was invaded by Plasma-Aliens. It had been quite a few years since the Justice Society of America had retired and there were relatively few superheroes around. A new hero named Triumph gathered together a group of heroes to stop the invasion. This group included Superman, J'onn J'onzz the Martian Manhunter, Flash II, Green Lantern Hal Jordan, Aquaman and Black Canary II. The heroes defeated the Plasma-Aliens, but during the fight, Triumph was caught in a temporal void and disappeared. Due to the temporal disturbance, the other heroes' memories of Triumph and the battle were wiped clean. It would be over a decade later before Triumph returned from the void.

Shortly after the Plasma-Aliens were defeated, a second group of aliens, from the planet Papilla, came to Earth. When the ruler of Papilla perished years before, a competition was declared to determine his successor. The claimants to his throne were sent to Earth, one each representing the dominant life forms of Papilla. Each of the life-forms "recruited" armies from the inhabitants of Earth, transforming people and animals into duplicates of their own form--stone, mercury, glass, bird-creatures, fire, wood, and crystal.

Working together, the most prominent heroes of Earth at the time defeated the menace from the stars. These heroes included the Martian Manhunter, Flash II, Green Lantern Hal Jordan, Aquaman, and Black Canary II. Although he also fought one of these aliens, Superman didn't actually meet up with the other heroes. The five assembled heroes decided to join forces as a permanent team to combat evil and uphold justice. They called themselves the Justice League of America, in part to honor the legendary Justice Society of America. The public acceptance of the JLA made it possible for many other heroes to go public at this time.

Flash became their first chairman. The team made its first headquarters in a mountain near Happy Harbor, Rhode Island in which they dubbed "The Secret Sanctuary." With the help of the United States government, the Sanctuary was equipped with a communications complex, aircraft hangar, pool, library, meeting room, lounge, kitchen, souvenir room, laboratory, and gymnasium.

Soon after that, a teenager from Happy Harbor, Lucas "Snapper" Carr, helped the JLA defeat Starro the Conqueror, a giant alien starfish. "Snapper" became the Secret Sanctuary's mechanic and computer technician became the team's mascot. Next, after assisting the team in a battle with Cottar the Weapons Master, Superman was offered membership. He turned down full-time membership but became an honorary reserve member, aiding the JLA on numerous occasions. 

The JLA continued to defend the Earth against many strange and powerful threats. They defeated Professor Ivo and his android Amazo who could mimic the abilities of each JLA member. They fought and vanquished the alien Despero for the first time. They protected the Earth from an invasion of beings from the magical dimension called Grimm world. And they triumphed over the alien Kanjar Ro and his "Slave Ship of Space."

Over the years the roster of JLA members grew continuously, as did its rogues gallery. Green Arrow  and Atom II were the next two members to join as the JLA battled menaces such as Dr. Destiny, Professor Amos Fortune, Felix Faust, the Lord of Time, the Demons Abnegezer, Rath and Gast, Dr. Light I, the Tornado Tyrant and Spaceman X. During this time, the Batman also joined under yet to be revealed circumstances.  His participation in JLA cases was inconsistent and when he did work with the League he would always take charge, regardless of who the chairperson was.

The JLA even teamed up with the recently reactivated the Justice Society of America to defeat the Crime Champions, a super-villain team made up of Chronos, Dr, Alchemy, Felix Faust, Fiddler, Icicle I, and Wizard. The JLA and JSA worked together on numerous cases in the next few years. Acting as a liaison between the JLA and JSA, the Golden Age Hawkman, and his wife Hawkwoman I, took part in many JLA cases. The League again battled Kanjar Ro, Despero, and Amazo and made new enemies like Headmaster Mind. The JLA and JSA defended the Earth from the Crime Syndicate, a group of super-powered beings from the anti-matter universe of Qward. Other JLA foes at this time included Brain Storm, the Key, the Unimaginable, the Royal Flush Gang, the Shaggy Man, T.O. Morrow, the Tattooed Man, and Aquarius, the villain responsible for killing the first Black Canary's father. The JLA even went up against the Clown Prince of Crime, the Joker. "Snapper" Carr resigned from the team when the Joker tricked him into betraying the JLA and revealing its secret headquarters. He has since redeemed himself and has maintained only occasional acquaintance with his former friends.

With the Secret Sanctuary's location exposed, the JLA soon enlisted the help of the United Nations to build a new headquarters. The constructed the Justice League Satellite which orbited 22,300 miles above the Earth. The JLA's newest headquarters boasted some tremendous resources. The greatest scientists on Earth used remnants of technology recovered from the various alien invasions over the years, combined with the technology of the Guardians of the Universe, to develop a teleportation device that the JLA used to bring members to the satellite from any place on Earth. The JLA Satellite contained living facilities for all the members. It had extensive facilities for monitoring events on Earth, and members were required to take turns serving 24-hour shifts on monitor duty. The JLA satellite also included a meeting room, souvenir room, laboratory, pool, computer room, gymnasium, dining facilities and sick bay.

With its new headquarters the JLA became a force to be reckoned with. They teamed up with the JSA to defeat Solomon Grundy; helped Deadman foil the plans of the League of Assassins; worked with Adam Strange to defend both Earth and Rann from the alien vampire Starbreaker, traveled through time with the JSA to rescue the time-tossed Seven Soldiers of Victory from the Iron Hand, fought Hector Hammond, recruited Red Tornado II and the Elongated Man as members; defeated the menace of Eclipso; battled the Injustice Gang of the World, which included the likes of Libra, Tattooed Man, Chronos, Scarecrow, Poison Ivy and Mirror Master I; fought old enemies like Amazo, Despero, Kanjar Ro, the Key, and the Shaggy Man; helped the JSA subdue their temporarily superhuman and insane teammate Sandy; battled the alien Manhunters for the first time with the aid of the mysterious alien woman named Willow; rescued the Red Tornado from the clutches of the evil robot Construct; met the Privateer; attended the wedding of the Atom; and even met, along with the JSA, heroes from other time periods like Miss Liberty, Jonah Hex, the Black Pirate and others.

Other heroes were invited to join the League during this time but rejected full-time membership including Adam Strange, Metamorpho, the Phantom Stranger, Black Lightning, Sargon the Sorcerer, Captain Comet and others. There are apparently quite a few untold JLA cases during this time as well. The JLA inducted Zatanna, who had worked with the team before, and Firestorm the Nuclear Man. The JLA had several encounters with the Secret Society of Super-Villains; Green Arrow quit the team for a short period of time; and the JLA and JSA met the New Gods and faced the threat of Darkseid for the first time. The League's old enemies like Starro, the Lord of Time, the Key, Amazo, T.O. Morrow and a new Secret Society of Super-Villains reared their ugly heads once more, only to be beaten by the JLA. During this era, the League was at its strongest.