Following the retirement of the old guard of the Justice Society of America, the nation endured a period of social repression and anti-heroic sentiment amidst the perils of the Cold War. But by the 1960s, a never-assassinated President John F. Kennedy is ready to lead the United States to the stars - a nation protected by the young super-heroes of the Justice League of America.
- Adam Strange
- The Atom
- Captain Marvel
- Green Arrow
- John Henry
- President John F. Kennedy
- Kid Flash
- Justice League of America
- Plastic Man
- This Earth is based on Darwyn Cooke's DC: The New Frontier, and is the direct continuation of the pre-Flashpoint Earth-21.
- John Henry was seen joining the champions of the Multiverse at the House of Heroes. It is unknown if this suggests he survived on this Earth, he was pulled from a divergent timeline, or if he was pulled forward from a point in time prior to his death; the appearance of some members of the Legion of Super-Heroes there suggests the latter may be a possibility.
- Earth 21 is opposite Earth 48 in the structure of the Multiverse.
- Earth 21 is part of the area in the local Multiverse termed "The Cartoon Rim" with Earths 12, 26, 42, and sometimes 16.
- Characters from Earth 21
- Other things related to Earth 21
- Earth 21's Comic Appearances
- Reality Gallery: Earth 21