A world almost entirely without metahuman beings (with the exception of Air Force Captain Allen Adam, transformed in the explosion of a U-235 powered engine into the quantum champion Captain Atom), this world's costumed heroes, made up of vigilantes and government agents, were assembled as the Pax Americana by the United States government in order to bolster national confidence after 9/11. However, in the wake of Captain Atom's disappearance, the defection of the ruthless and disturbed Question, and the assassination of President Harley by the Peacemaker, the concept of "the American super-hero" may be doomed on Earth 4.
- Pax Americana
- Blue Beetle I
- Nightshade I
- President Harley
- Vice-President Eden
- Sarge Steel
- George W. Bush
- John F. Kennedy
- Earth 4 is based on the earlier concepts of Earth-Four and Earth-4, as well as spiritual influence (by the admittance of Earth 4's creator, Grant Morrison) from Watchmen, itself largely based on the Charlton Comics characters featured on Earth 4.
- The adventures of this Earth are published on the other worlds of the Multiverse under the Quantum Comics banner.
- Earth 4 is opposite Earth 42 in the structure of the Multiverse, and is the closest known universe in it to the Underworld.
- Earth 4 is part of the area in the local Multiverse termed "The Otherworlds" with Earths 35, 39, 41, 45 and 46.
- Earth 4 possesses hydrogen-powered cars (such as the "Ford Hydro" model) refueled at "gas garages".
- "Beetle Brand" protective clothing is popular on Earth 4, pioneered by Ted Kord based on innovations to his own Blue Beetle uniform.
- "Atomade" is a popular energy drink on Earth 4.
- Popular video games on Earth 4 include PAX INFANTRY 4: LUNAR JIHAD, BATMAN: PLANET ARKHAM and HUB CITY RACER.
- Both JLA: Earth-2 and All-Star Superman have been published on Earth 4, as well as Major Comics publications such as Major Max.
- Characters from Earth 4
- Other things related to Earth 4
- Earth 4's Comic Appearances
- Reality Gallery: Earth 4