The Multiverse was a much darker place during the “Bronze Age”. It features both Silver and Bronze-Age heroes on Earth-One and Golden Age heroes who were recently retconned to Earth-Two
1971 Oliver Queen (Green Arrow)’s sidekick Roy Harper (Speedy) gets addicted to Heroin - Green Lantern/Green Arrow vol. 2 #85-86
1970 Kara Zor-El/Linda Lee Danvers (Supergirl) looks at costume choices. -Adventure Comics vol. 1 #397
1970 Kara Zor-El/Linda Lee Danvers (Supergirl) gets a new costume from Wonder Woman’s boutique
1971 Jack Kirby’s Fourth World saga introduced the “New Gods” who would be very popular -New Gods vol. 1 #1
1972 Kara Zor-El/Linda Lee Danvers (Supergirl) in her new hot pants costume in -Supergirl Vol-1 #1-10
1973 The pre-Zero Hour Original Legion of Super-Heroes get their own book-Legion of Super-Heroes vol. 1 #1-4
1974 Selena Kyle (Catwoman) with tail –Batman vol. 1 #256
1975 Selena Kyle (Catwoman) returns to her original Purple Dress and Green Cape -Batman vol. 1 #266
1976 On an alien planet in the Earth-One universe a young slave girl Mollachon (Starfire II) aka "The Siren of Sword and Science" aka "Wondrous Warrior" fights with a sword. -Starfire vol. 1 #1-8
Mollachon (Starfire II) on the cover of –Starfire vol. 1 #8
1976 Duela Dent (Harlequin) calls herself “Joker’s Daughter”. She is actually from Earth-Three, and is the daughter of “The Jokester” and Evelyn Dent (Three-Face) -Batman Family #6
1976 Kara Zor-L travels from Krypton-Two to Earth-Two and becomes Karen Starr (Power Girl). She is Kal-L’s cousin, and is older than Earth-One Kara Zor-El (Supergirl). This issue also re-introduced the Justice Society of America, especially some younger members, serving as an auxiliary known as the All-Star “Super Squad” –All-Star Comics vol. 1 #58-74
1977 Wonder Woman does an unlikely back-bend on an Alternative Cover -Wonder Woman vol. 1 #231-A
1977 Earth-Two Helena Wayne (Huntress II) is daughter of Earth-Two Bruce Wayne (Batman) and Earth-Two Selena Kyle (Catwoman). -DC Super-Stars vol. 1 #17
Earth-Two Selena Kyle (Catwoman) dies in Earth-Two Bruce Wayne (Batman)’s arms in this issue. -DC Super-Stars vol. 1 #17
Earth-Two Helena Wayne becomes “the Huntress” in order to bring Justice to the people who caused her mother’s death. -DC Super-Stars vol. 1 #17
1977 Earth-One Shayera Hol (Hawkwoman I) (from Thanagar) finally joins the Justice League. –Justice League of America vol. 1 #146
1978 Earth-Two Kal-L/Clark Kent (Superman) is retconned to have revealed his identity to Earth-Two Lois Lane and they are married –Action Comics vol. 1 #484
1978 Death of Earth-Two Bruce Wayne (Batman)
Seen 4 ways in -Batman vol. 1 #291-294
1978 New Earth Henry Heywood Sr. (Commander Steel I) -Steel the Indestructible Man vol. 1 #1
Earth-Two Helena Wayne (Huntress II) is “step-brother” of Earth-Two Richard Grayson (Robin)
1978-1982 Earth-Two Helena Wayne (Huntress II) travels to Earth-One several times and calls Earth-One Bruce Wayne (Batman) “Uncle Bruce” because he reminds her of her dead father, Earth-Two Bruce Wayne (Batman)
1979-1980 Stacy Macklin (Lady Lunar) appeared in Wonder Woman, Adventure Comics, World’s Finest and Superman vol. 1 #339
1980 Earth-One Ellen Leeds (Supergirl) picked up some X-Krypton when she found Kara Zor-L in her Kryptonian rocket. Ellie's powers manifested in only one issue where she teamed up with the real Supergirl. –Superman Family vol. 1 #203
1980 The Earth One Pre-Crisis, Pre-Zero Hour Original Legion of Super-Heroes lose Kal-El (Superboy) and go out on their own. -Legion of Super-Heroes vol. 2 #259-354
1980 New Earth Wallace “Wally” West (Flash III) aka (Kid Flash I) originally has a costume identical to the adult Barry Allen (Flash II) but eventually gets different colors as shown here. –Flash vol. 1 #110
1980 Koriand'r (Starfire III) aka Kory Anders - and the entire "New Teen Titans" first appearance - DC Comics Presents vol. 1 #26 followed by New Teen Titans vol. 1 #1
1981 The Golden Age New Earth Justice Society of America are loosely re-formed for an “earth-two style” WWII story featuring Hawkman, Johnny Quick, Liberty Belle, Robotman, Plastic Man, Doctor Fate, and may more –All Star Squadron vol. 1 #1-67
Hawkman: Golden Age Earth-Two Carter Hall (Hawkman) and Silver Age Earth-One Katar Hol (Hawkman) were retconned to be the same person.
1981 Silver Age (1955) Bruce Wayne (Batman) and Selena Kyle (Catwoman) get married and Selena becomes Selena Wayne. Retconned in -Superman Family vol. 1 #211
1982 Leonid Konstanovich Kovar (Starfire I) changes his name to “Red Star” because the New Teen Titans already have K’oriandr (Starfire III) -New Teen Titans vol. 1 #18
1982 - 1984 -The Daring New Adventures of Supergirl vol. 2 #1
1983 Lyla Michaels (Harbinger) –The New Teen Titans vol. 1 Annual #2
1983 Selena Kyle (Catwoman) in her Purple dress and Green cape -Batman vol. 1 #355
1983 Infinity Inc. is formed on Earth-Two by children of JSA members who were not able to join the JSA. Infinity Inc. is similar to JLA/Teen Titans on Earth-One. The team included son of Hawkman and Hawkgirl, Hector Hall (Silver Scarab), Fury II, Northwind, Nuklon, Jade, Obsidian, Power Girl, Huntress, and Brainwave Jr. -All-Star Squadron vol. 1 #25 and Infinity Inc. vol. 1 #1
1988 Earth-Two Hector Hall (Silver Scarab I) dies and is resurrected as (Sandman II) - Infinity Inc. vol. 1 #49 then marries pregnant Earth-Two Hyppolyta “Lyta” Trevor-Hall (Fury II). - Infinity Inc. vol. 1 #51
1983 Kristin Wells (Superwoman) traveled back in time from the 29th Century to see who Superwoman is. She learned that Superwoman was herself. -DC Comics Presents vol. 1 Annual #2
1984 A new costume for Kara Zor-El/Linda Lee Danvers (Supergirl) in The Daring Adventures of Supergirl Vol-2 #13
1984 The Justice League is dissolved by Aquaman - and soon forms again in Detroit as Justice League of America: Detroit - adding young heroes Vibe, Steel, Vixen, and Gypsy. It also includes Aquaman, Elongated Man, Zatanna, and Martian Manhunter - Justice League of America vol. 1 Annual #2 and Issue #233-236
1984 Earth-One Pre-Crisis, Pre-Zero Hour Original Legion of Super-Heroes (without Superboy) in -Legion of Super-Heroes vol. 3 #1-63
1985 Earth-Two Jonni Thunder has a parasitic alien named Mzzttexxal (Thunderbolt) and is also seen in Post-crisis New Earth. -Jonni Thunder AKA Thunderbolt vol. 1 #1-4
1985 Marcie Cooper (Harlequin) -Infinity, Inc. vol. 1 #14
Earth Two and the rest of the multiverse is mostly destroyed. Parts are merged into Earth One which is re-named “New Earth”
In the 1980's, DC realized that their multiverse needed fixed. It had become too complex for most readers to follow. The solution was Crisis on Infinite Earths. The story changed everything, and became the great hinge that folded all the earths and most of the characters (the ones who survived) into one big unified universe which would eventually be known as "New Earth" or "Prime Earth". Many characters were folded in, and many were ejected or simply erased from history -such as Superboy and Supergirl. Major characters were given new origins.Wonder Woman, Batman and Superman were all retconned, and the Superman book was re-launched as #1.
Although the Justice Society of America were originally introduced during DC's Golden Age Earth-Two era, their existence following Crisis on Infinite Earths remains intact. The characters may have existed on both earths - as members of the JSA on Earth-Two and of the JLA on Earth-One, but the JSA is now considered to have only existed in the golden age of New Earth.
Wonder Woman is retconned out of the pre-Crisis JLA.
Earth-Two Huntress (Helena Wayne) and Earth-Two Dick Grayson (Robin) die and disappear from existence.
New Earth Yolanda Montez (Wildcat II) takes over for Golden Age Earth-Two Ted Grant (Wildcat I) when he becomes crippled. -Crisis on Infinite Earths #6
Earth-One Headband-wearing Kara Zor-El (Supergirl) is killed and retconned out of existence. She doesn't return until 2004
Earth-Two Kal-L and Earth-One Kal-El shown here together.
By DC editorial fiat, “New Earth Kal-El (Superman) is the only survivor of Krypton”. Therefore, Earth-Two Kal-L (Superman), Earth-Prime’s Kal-El (Superboy-Prime) and Earth-Two Lois Lane-Kent, who can't exactly be erased from history, are moved to the “Paradise Dimension” (the Pocket Universe)
Finally, The Multiverse is destroyed and all the various Kryptonians with it (except Earth-One Superman). The Big Bang creates a new unified universe called “New Earth” (and an anti-matter universe).