In DC Comics, the Multiverse was a continuity construct in which multiple fictional versions of the universe existed in the same space, separated from each other by their vibrational resonances. Each universe in this multiverse varied from the others, in either subtle or profound ways.

In particular, the Earth of each universe had a different set of superheroes, or the life histories of its superheroes were different from those of others'. In several cases, characters from other publishers acquired by DC - previously established as a part of a fictional universe of their own - were assigned their own alternate universe within the Multiverse. The universes were identified by referring to the alternate Earths, known as "Earth-One", "Earth-Two", "Earth-Three", "Earth-X", and so forth. The first such parallel world was introduced in 1961 in The Flash #123, in the story "Flash of Two Worlds". They were eliminated in Crisis on Infinite Earths, a mini-series published in 1985.

Earth-One

Home of DC's Silver Age heroes, including the original Justice League of America. In this world, Superman had a career as Superboy while in his teens, and an array of other superheroes first appeared in the 1950s or later. The Flash was police scientist Barry Allen, Green Lantern was galactic peacekeeper Hal Jordan, Hawkman was Thanagarian Katar Hol, and the Atom was shrinking scientist Ray Palmer. Characters unique to this world included the Martian Manhunter, Elongated Man, Firestorm, the Guardians of the Universe and Green Lantern Corps, the Teen Titans, the New Gods, and most other heroes introduced by DC in the 1960s and 1970s. As the default Earth for most of DC's comics during the prolific Multiverse era, this was by far the most "populous" and greatly explored.

Earth-Two

Home of DC's Golden Age heroes, including the Justice Society of America. In this world, Superman, Batman, and Wonder Woman began their careers as adults at the dawn of World War II (concurrent with their first appearances in comics). The Flash was chemistry student Jay Garrick, Green Lantern was magic-powered Alan Scott, Hawkman was archaeologist Carter Hall, and the Atom was short powerhouse Al Pratt. Characters unique to this world included the Star-Spangled Kid, Huntress, The Spectre, Johnny Thunder, Dr. Fate, and Mr. Terrific. The heroes of this world appeared as comic book characters on Earth-One (subconsciously channeled by Earth-One's writers).

Earth-Three

Home of evil versions of Earth-One heroes, including the Crime Syndicate of America. In this world, history was "backwards": Christopher Columbus was an American who discovered Europe; Britain fought and won its freedom from the United States in the Revolutionary War; President John Wilkes Booth was assassinated by actor Abraham Lincoln; the United States flag had "reversed" colors (black stars on a red background, and alternating blue and black stripes); and so on. Noteworthy characters include Ultraman (Superman), Superwoman (Wonder Woman), Owlman (Batman), Power Ring (Green Lantern), Johnny Quick (Flash), and Alexander Luthor (a heroic version of Lex Luthor).

Earth-Four

Home of the former Charlton Comics heroes. This world was introduced at the beginning of Crisis and did not survive; several of its heroes did. Noteworthy characters include Captain Atom, Blue Beetle, Nightshade, Peacemaker, The Question, Peter Cannon, Thunderbolt, and Judomaster.

Earth-Six

Home of Lady Quark and Lord Volt. On this Earth, America lost the Revolutionary War, and was apparently ruled by a royal family of superheroes. Given its appearance, technology seems to have progressed faster on this world as well. It was destroyed in Crisis, with only Lady Quark surviving.

Earth-Twelve

Home of the Inferior Five. Noteworthy characters include Awkwardman, Blimp, Dumb Bunny, Merryman, and White Feather. This world may have been home to other comedic superheroes published by DC.

Earth-A

Home of the Lawless League . This world was created by Johnny Thunder's evil counterpart from Earth-One when he unwisely altered the origins of the Justice League. "A" stood for "alternate", since it was an alternate version of Earth-One. The heroes of this world included alternate, evil versions of Superman, Batman, the Flash, Green Lantern, and the Martian Manhunter -- the evil Johnny Thunder's criminal henchmen, granted powers and skills identical to the Justice League's members.

Earth-B

This world was never officially established, but is often cited as the setting for team-up stories told in The Brave and the Bold which did not always conform to established continuity for Earth-One (or any other established Earth). (For instance, one such story featured Catwoman committing murder, which neither the Earth-One nor Earth-Two versions would ever do - it was strictly against her moral code.) Notable characters include Batman (who appeared regularly in the series).

Earth-C

Home of the Zoo Crew. This world is populated with anthropomorphic animals. Notable characters include Captain Carrot, Alley-Cat-Abra, Fastback, Little Cheese, Pig-Iron, Rubberduck, and Yankee Poodle.

Earth-C-Minus

Home of animal superheroes Justa Lotta Animals , a comic written by Captain Carrot of Earth-C.

Earth-D

Home of the Justice Alliance of America . This world appeared in Legends of the DC Universe as a previously-untold chapter of Crisis published more than a decade after the fact. It featured a more ethnically diverse version of several Earth-One heroes, with no major tragedies in the heroes' lives (not counting the Crisis, of course). As such it was a combination of modern multi-cultural sensibilities combined with Silver-Age-style innocence.

Earth-Q / Earth-Quality

Home of the Freedom Fighters and Kid Eternity as they were originally published by Quality Comics in the 1940s (i.e. not the later versions published by DC, set on Earth-X and Earth-S). Not officially identified.

Earth-S

Home of the former Fawcett Comics heroes, including the Captain Marvel (Shazam!) family. Other noteworthy characters include Bulletman , Bulletgirl , Ibis the Invincible , Spy Smasher , Mister Scarlet and Pinky , and Commando Yank .

Earth-X

Adopted home of several former Quality Comics heroes, including the Freedom Fighters. On this world, Nazi Germany won World War II, and the Freedom Fighters - originally from Earth-Two - fought to defeat them. Noteworthy characters include Uncle Sam , the Human Bomb, Miss America, The Ray , Black Condor , Doll Man, Phantom Lady, Firebrand , and the Red Bee.

Earth-Prime

Home of few or no superheroes; this was supposedly "our" world, where the characters of Earth-One were merely comic book characters (the continued existence of the real world following the destruction of Earth-Prime in Crisis suggests that it was not, in fact, our world). DC editor Julius Schwartz lived here, and met the Flash of Earth-One who visited this world. The little-used character Ultraa was described as the only superhero of this world. In a story just before Crisis on Infinite Earths, a young Clark Kent of this world discovered that he had super powers and became Superboy; at the climax of Crisis, he joined the Superman and Lois Lane of Earth-Two (the originals) in a kind of paradise.

Other Earths

Various other Earths were arguably depicted in DC's substantial publishing output during the period in which the Multiverse was in effect. Identifiers such as "Earth-Five" or "Earth-K" have been coined by fans and applied to certain characters and stories. Some Earths have been posited to explain (for example) Superman Jr. and Batman Jr. (the teenage sons of the two heroes who appeared in a handful of stories and cannot be reconciled with any known Earth) or the Super Friends (based on the TV series). On yet another conjectured Earth, the Silver Age DC Comics heroes lived side-by-side with the Silver Age Marvel Comics heroes, and it is on this alternate Earth where various team-ups and battles between the two publishers' heroes have occurred over the years. Some of these could instead be categorised using the "imaginary story" identifier which DC occasionally applied to stories they didn't wish to be considered part of continuity, especially before the invention of the Multiverse.

Contact between universes

Most inhabitants of the Multiverse were completely unaware of the other universes. The first character to cross the gap between them was Barry Allen, the Flash of Earth-One, who accidentally vibrated at just the right speed to appear on Earth-Two, where he met Jay Garrick, his Earth-Two counterpart.

Other characters with super-speed powers were able to duplicate the trick, but it was not often done. Magic and technological devices could do the job as well. The Justice League's "transmatter" device (ordinarily used to transport between their satellite headquarters and the ground), was pressed into service for annual events in which the League and some of their counterparts on other Earths faced a universe-crossing "crisis" of one sort or another. Writers occasionally put characters from different Earths together in the same story without explanation, a continuity error often cited as a reason for eliminating the Multiverse in Crisis.

Pre-Crisis

Characters, events and other elements established before Crisis (especially those eliminated by it) are considered "Pre-Crisis". All Characters in Pre-Crisis exist in the Multiverse.

Crisis

The Multiverse was destroyed in the "maxi-series" Crisis on Infinite Earths, by a villain known as the Anti-Monitor. One by one, it invaded each universe and destroyed it. The heroes of Earth-One and Earth-Two, with several survivors from other Earths, managed to hold off the destruction of these last two universes long enough to defeat the Anti-Monitor. The two were merged into a single universe with its own history combining elements of the two with completely new elements. For example, there was a Flash named Jay Garrick in the JSA during the 1940s, and another Flash named Barry Allen in the JLA during the 1960s. But Superman had a completely new history, different from the Superman of Earth-One or Earth-Two.

Post-Crisis

Some fans refused to accept that the Multiverse no longer "existed" after Crisis, and posited that the "Post-Crisis" DC Universe was merely another alternate universe within the Multiverse, sometimes dubbed "Earth-Zero" or "Earth-PC".

Although DC did not relent on their position that the other Earths no longer existed (and had "never" existed), they published occasional one-shots and mini-series labeled "Elseworlds", many of which would have been consistent with the concept of the Multiverse. But DC officially classified these are stories that perhaps "could have" happened, but had not. They maintained that there was only one canonical Earth in the DC Universe. Although never labelled as "Elseworlds" tales, Stan Lee's reimagining of DC heroes, and graphic novels such as Kingdom Come and Dark Knight Returns, which diverge from established continuity, could be said to also reflect the "Elseworlds" concept.

DC relented somewhat with the introduction of Hypertime, which provided a conceptual framework to recognize both canonical and apocryphal stories. It was arguably a superset of the Multiverse, including not only the whole range of pre-Crisis stories set on alternate Earths, but any story set in any continuity.