See the discussion on the post-Crisis DC Earth.
"At what point DC began chronicling the adventures of Earth-One heroes, rather than Earth-Two heroes, cannot be determined. The Martian Manhunter appeared first in DETECTIVE COMICS #225, cover-dated November, 1955. But Captain Comet, who has been shown to be an Earth-One hero, first appeared in STRANGE ADVENTURES #9, June 1951. Batman of Earth-Two is said to have married his Catwoman in 1955, making it improbable that any of his adventures were chronicled in BATMAN, DETECTIVE COMICS and WORLD’S FINEST COMICS from that year onward. But Superman of Earth-Two is said to have married Lois Lane by 1953, in SUPERMAN FAMILY. As an indexer, my rule of thumb is that everything published post-November 1955, unless specifically labelled otherwise, occurs on Earth-One, which some earlier comics (such as STRANGE ADVENTURES) chronicling earlier Earth-One adventures."
"Superboy, who, at various times has been depicted living in the 1930s, the 1940s, the 1950s and even the late 1960s, is definitely an Earth-One character. It has been stated repeatedly in 1970s DC Comics that Kal-L of Earth-Two had no Superboy career, even though a later story showed a time-and-dimension-lost Superboy of Earth-One training a young Clark Kent of Earth-Two in the use of his super-powers. Thus, the first Superboy story, in MORE FUN COMICS #101, Jan.-Feb. 1945, may have claim to the title of earliest Earth-One story published by DC."
"But, even though Superboy/Superman was undoubtedly the most famous super-hero in the Earth-One universe, he was not the first. The Shadow, active during the early 1930s, preceded him. It was though, until recently that heroes such as Zatara, the Guardian, and Manhunter (Paul Kirk) were native to Earth-One, but their use in ALL-STAR SQUADRON and Roy Thomas' subsequent claim that these heroes later moved to Earth-One puts this in question. Since the Crisis, of course, the question may well be moot."
Other Golden Age heroes who were resident on Earth-One include Air Wave, Commander Steel, Robot Man and Zatara these have all had contact with second generation heroes. The Guardian (and necessarily) the Newsboy Legion had counterparts on Earth-Two while heroes such as Doc Savage, Tarzan and the Shadow have been published by so many people that they could exist on nearly any Earth. The mystic Sargon the Sorcerer later showed up in the JLA title.
"The coming of Superboy heralded the dawning of the true Heroic Age on Earth-One, however. His generation of contemporaries were the most famous super-champions in his Earth's heroic history. Aquaboy, the young Aquaman, was his contemporary. Others of his age had to wait till they reached maturity, and then came Batman, Green Arrow I, Wonder Woman, J'onn J'onzz. From 1955 through 1961, their most famous contemporaries joined them: Hal Jordan became the Green Lantern; Katar Hol came from the planet Thanagar with his wife Shayera, to become Hawkman and Hawkgirl; Ray Palmer, finding a white dwarf fragment, created the Atom uniform; four men living on 'borrowed time' became the Challengers of the Unknown; scientist Rip Hunter broke the time barrier; and the Justice League of America was established. They were hardly the last of the Earth-One heroes but certainly the most famous."
"In 1961, while entertaining a theatre-full of children, the Flash (Barry Allen) attempted a disappearing rope-trick and so vibrated his body that he reached the correct frequency to disappear from the Earth-One plane and reappear on Earth-Two. There he found himself in Keystone City, home to his comic-book idol, the Flash, alias Jay Garrick. Locating Garrick and his wife Joan, the Flash of Earth-One revealed his existence to them and with it, the existence of a parallel Earth. (Later revelations in ALL-STAR SQUADRON have made it clear that the Flash and the rest of the Justice Society were aware that parallel Earths existed, but, perhaps, not specifically Earth-One)."
"Thus began a frequent series of double-Flash team-ups which resulted in the revival of the Justice Society of America and their inevitable teaming with the Justice League. It was revealed in DC COMICS PRESENTS Annual #1 that, since Barry Allen had made the 'first' crossing from one Earth into another, his world was designated Earth-One and Jay Garrick's was called Earth-Two by those in the know."
"Earth-One's history progressed apace throughout the Sixties, Seventies and early Eighties. The Doom Patrol was born - and died. Bruce Gordon became afflicted with his evil persona, Eclipso. The Teen Titans were formed. A new hero, Metamorpho, came into being and rejected Justice League membership. Boston Brand, after death, became the wraith Deadman. Jack Ryder happened upon the Creeper's identity. Alec Holland, a biochemist, was killed and replaced by the Swamp Thing... and so on. Earth-One heroes came into contact annually with heroes from parallel Earths. Naturally, more is known of Earth-One's history from 1955 to 1986 as the 'basis' for DC's new Earth."
"In 1985, a 'crisis' of a different kind than what actually occurred would have happened. In this scenario, Earth would undergo a time of war which would either result in the Great Disaster of Kamandi's time, or the Legion of Superheroes in an alternative thirtieth century. (Actually, in the original scenario, both happened). Other divergent futures were depicted: the time-line in which Green Lantern becomes Solar Director of a future Earth; the one in which Iris West is born to future parents and sent back to Barry Allen's time; the one in which a descendant of Clark Kent becomes Superman in 2965. All of this was changed by what actually took place in 1985 in the DC Universe - the Crisis on Infinite Earths."
When the heroes of the Justice League gained their own cartoon show in the form of the Super Friends it was inevitable that they would in turn spawn a spin off comic called THE SUPER FRIENDS. Written by E. Nelson Bridwell the stories while possibly meant to be in Earth-One were a little to different for inclusion there. This Earth saw the first appearance of the various heroes that would go onto become the Global Guardians (a real Earth-One group). This Earth was set aside from Earth-One by the inclusion of Earth-Two characters such as Plastic Man and T.N.T and Dyne-Mite.
"While World War I was entering its closing years on Earth-Two, the planet Krypton Two was exploding. Jor-L sent his only son Kal-L to safety in a rocket just before his planet was destroyed. Kal-L was adopted by John and Mary Kent and raised to live as an Earthman and to conceal his mighty powers, which he would someday use for the cause of justice. Upon their deaths circa 1938, Kal L alias Clark Kent, became the original Superman, prototype for all the heroes that came after him."
"Superman was not the first super hero of sorts on Earth-Two, Doctor Occult having scooped him (at least in an active career) by some three years. He was succeeded, on October 31, 1938, by the Crimson Avenger, a non superpowered hero. Then came Batman, the Sandman I, Doll Man, Doctor Fate, Uncle Sam, Midnight, the Human Bomb, The Spectre, Wonder Woman, the Black Condor, Johnny Thunder, the Flash, Liberty Belle, Johnny Quick, the Green Lantern. . . not only those appearing in the DC Comics of the 1940s, but also those whose exploits were depicted in Quality Comics. (This last was revealed in the Eighties in All-Star Squadron.)"
"In 1940, the attempted invasion of Britain by the Nazis brought the Justice Society of America into being. Then, in the wake of the Pearl Harbour bombing, virtually all the super heroes in America became members of the All Star Squadron. Some of these were siphoned off by Uncle Sam to become the Freedom Fighters, who battled the Nazis on the parallel Earth X where the Axis won World War II. But on Earth-Two, as on most other Earths, the Allies defeated Hitler and his minions, and the All Star Squadron presumably disbanded following V J Day. The Justice Society continued as a fighting unit until 1951, when Senator O'Fallon caused them to resign after questioning their vigilantism. Superman, Batman, and Wonder Woman remained semi-active throughout most of the Fifties, each of the three getting married eventually."
"In 1961, Jay Garrick, the Flash, was visited by Barry Allen, the Flash of Earth-One. Barry's visit coincided with a crime spree conducted by the Shade, the Fiddler and the Thinker, and both Flashes teamed up to bring the villains to justice. Jay returned to semi-active status as the Flash after the adventure. Within two more years he was joined by the bulk of his Justice Society comrades. (Several Earth-Two heroes, such as Zatara and Robotman I, were said to have moved to Earth-One earlier. . . presumably without the knowledge of the Justice Society members. Other All Star Squadron alumni not in the JSA may have died or simply stayed retired in the interval.) Several JSA members were kidnapped by Vandal Savage in 1963. Not long after that, the Justice Society teamed with the Justice League for the first time to defeat the Crime Champions, a team of villains culled from both Earths. When it was discovered that their Earths became particularly accessible to each other at that certain time, they began a practice of continual team ups every years, even travelling to other Earths in the process."
"The Seven Soldiers of Victory, a 1940s hero team similar to the Justice Society, had become lost in time somewhere in the early 1950s and were rescued in 1972 by the JLA and JSA. Robin had already become an adult crime fighter and taken Batman's place in the Justice Society by this time. He was joined, four years later, by the Star Spangled Kid of the Seven Soldiers and by Power Girl, the counterpart to Earth One's Supergirl, in a short lived Super Squad of young heroes which was gradually amalgamated into the Justice Society. The JSA assumed an increasingly active status during the 1970s, culminating in the deaths of Mr. Terrific and Batman."
"Then, in 1983, the existence of the offspring or godchildren of several JSA members was revealed. Together with the Star Spangled Kid, Power Girl, the Huntress (Batman's daughter), and Brainwave, Jr., son of the JSA's greatest enemy, they formed Infinity Inc., an updated and improved Super Squad. Infinity, Inc. continues to this day, not so much a successor to the Justice Society as an entirely different sort of team."
"Earth Two had several future time lines revealed, including one in which Brane Taylor became the Batman of the 30th Century and one from which the "last criminal," Knodar, returned to bedevil Green Lantern. All of these time lines have been subsumed into the one time line of the new DC Earth (since July of 1985), meaning that events shown in earlier DC comics pertaining to them have been altered or eliminated. "
There was a period between the ending of the Golden Age and the Silver Age where distinct stories were published that were neither part of Earth-One or Earth-Two, the majority of these adventures can be reasoned to have happened on Earth-E. However Earth-E is in many forms a proto-Earth-One and so the initial changes that occurred there are represented hero. There is no Superboy in Earth-Two but a Superboy could well have existed on this Earth.
The third Earth was the home to evil versions of the Justice League members, in the form of the Crime Syndicate: Ultraman (Superman), Power Ring (Green Lantern), etc. This group of villains would battle the Justice League time after time. In the post crisis universe it has been stated that the evil counterparts actually came from the Anti-Matter universe. If the heroes are villains then it follows that the villains are heroes, so in this world Lex Luthor III was actually a good guy and helped the Justice League defeat their counterparts. Traces of this Lex Luthor can be found in the Luthor from the Pocket Universe that was created by the Time Trapper in post-crisis and pre-Zero Hour comics.
In the SUPERMAN FAMILY title there was a back up strip featuring "Nightwing and Flamebird" (Van-Zee and Ak-Var rather than Superman and Jimmy Olsen). The battled a Kandorian crime lord who was revealed to by Jur-Ll an evil counterpart of Jor-El whose Krypton never exploded. Michael Norwitz suggests that this could have plausibly been Ultraman's father.
"This Earth has only recently come within the bounds of the DC comics Multiverse; prior to 1985, its heroes were the property of Charlton Comics. Their most famous crusaders were Captain Atom, the Blue Beetle II, Nightshade, Thunderbolt, Son of Vulcan, the Question, and the Peacemaker, all of whom originated in the 1960s."
"There have been heroes who predated the Silver Age Earth Four group, but very few of them. It is possible that the Hercules who starred in his own Charlton Comics series is indigenous to Earth Four, and he may have been one of the Olympians who helped create the Son of Vulcan. The Gunmaster, a masked hero, helped preserve justice in the Old West of Earth Four with a young sidekick named Bullet. Judomaster helped fight the Japanese invaders in the Pacific during World War II, before being yanked into the present by the time warping effects of the Crisis. The Olympians, for a brief time, endowed a youth with power over fire, earth, air, and water, turning him into Nature Boy in the 1950s. Other short lived heroes, such as Mr. Muscles and Zaza the Mystic, appeared in the decade preceding the new era of super crusaders, and even Ibis and the Golden Age Blue Beetle appeared in some Charlton Comics. But the latter two cases probably only depicted incidents happening on Earth-S and on Earth-Fox, respectively."
"When Captain Nathaniel Christopher Adam became Captain Atom in 1961, he ushered in the new age of heroes on Earth-Four. He was followed some three years later by Earth Four's first Blue Beetle, Dan Garrett, an archaeologist who gained super powers from a mystic blue scarab. They were joined within three years by the Son of Vulcan, an American who was endowed with the might of the Olympian gods; by Thunderbolt, who had been trained by Tibetan monks to harness the energy of his entire brain to perform amazing feats; the new Blue Beetle, who lacked super powers but followed in the footsteps of the dead Dan Garrett; the Sentinels, a trio of youths who were given super abilities by special devices; the Peacemaker, a diplomat who devised weaponry to be used against the perpetrators of war, the Fightin' Five, a team of specialists who fought would be world conquerors; the Question, a crusading reporter who ferreted out facts by assuming a faceless identity; and the lesser known Shape, Tyro Team, and Spookman, all of whom had only one adventure apiece depicted in Charlton Comics. Nightshade, the daughter of a United States Senator and an other dimensional princess, had the power to become a living shadow, besides her considerable martial arts expertise, and became first the partner of Captain Atom and then a solo heroine in her own right."
"The history of Earth-Four was, of course, considerably changed when it was merged with four other Earths in the Crisis. Earth-Four also possessed several different future time lines. In one of them, the Prankster, a harlequin like hero, fought against a repressive world-wide dictatorship. In another, a duo named 13 and Jinx came to 1967 to stop Captain Atom's enemy, the Ghost, from endangering their time line. But these and any other possible Earth-Four futures have been altered and subsumed into the future time lines of the new DC Earth, and, if they exist, do not do so exactly as previously depicted."
Supposedly an Earth that appeared in the opening pages to Crisis #1.
The sixth Earth first appeared in the Crisis on Infinite Earths crossover, it is a global monarch that was ruled by the partners Lady Tashana Quark and Lord Karak Volt with their daughter Princess Liana Fern. All three were born with natural superpowers. This world was destroyed by the waves of antimatter unleashed by the Anti-Monitor. In the reformed DC universe Earth-Six was just a planet in uncharted space that was destroyed in the Crisis, Lady Quark is the only known survivor.
"Earth-12 is the world on which the Inferior Five live, and, possibly, where all the DC humour comics not involving funny animals occur. Earth-Twelve has its own Plastic Man and Superman, as shown in issues of Inferior Five, and, if Jerry Lewis's comic adventures take place there, it also boasts its own Flash, and Wonder Woman. If the I5's statements in one issue that the Justice League, the Doom Patrol, and the Teen Titans could outdo them is taken literally, that could establish more parallels. A songwriter who visits the I5 in one issue claims to have written fight songs for all these teams and also for the Blackhawks, the Sea Devils, and the Legion of Super Heroes (he is shown being kicked out of the Legion clubhouse by Invisible Kid). DC's Plastic Man of the 1960s undoubtedly lives on Earth-Twelve, which would underscore the feasibility of his cameo in an Inferior Five adventure."
"The heroes who helped fight World War II on Earth-Twelve were the Freedom Brigade, a group of superhumans who intermarried upon retiring and had children who, as Merryman, the Blimp, Awkwardman, Dumb Bunny, and the White Feather, formed the Inferior Five. During their careers, they encountered several bizarre dopplegangers of Marvel heroes, such as a red bearded Thor, the Egg's Men, the Kookie Quartet, Man Mountain, Prince Nabob the Sunk Mariner, the Cobweb Kid, and Iron Pants. Thus, it is possible that Earth 12 is a skewed version of Crossover Earth. (Its Marvel Universe counterpart is Earth Marble, as presented in Not Brand Echh.) "
"Earth-Twelve was destroyed in the Crisis, and the Inferior Five were shown tumbling into the dimensional world of Oz in Oz Wonderland War #3 and later appeared in Crisis on Infinite Earths #12. The last appearance implies that the Inferior Five still survive, trapped on an Earth they never made, which will probably never make sense of them (except in Plastic Man's Acme City)."
Grant Morrison in his early run on Animal Man, referenced a lot to the Crisis and at one stage, a character is shown a purple butterfly and is told that it came from Earth-Fourteen.
Overman et al (numbered as such by Morrison in an AMAZING HEROES PREVIEWS SPECIAL).