Multiverse (Post-52) - Earths:

• 0 • 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 • 26 • 27 • 28 • 29 • 30 • 31 • 32 • 33 • 34 • 35 • 36 • 37 • 38 • 39 • 40 • 41 • 42 • 43 • 44 • 45 • 46 • 47 • 48 • 49 • 50 • 51 •
• Earth-Prime • Limbo • Antimatter Universe •

• In the original Multiverse, Earth-Prime was presented as the "real" Earth, the actual reality where the readers lived, DC Comics operated as a publisher and all superheroes are fictional.Eventually it was stated that the writers of DC Comics of Earth Prime unconsciously base their stories on the adventures of the heroes on Earth-One and Earth-Two.
• After the Crisis, a duplicate of the original Earth-Prime universe was first seen at the end of Final Crisis: Legion Of 3 Worlds. How, exactly, this new Earth-Prime was created remains unclear. It may have existed (unseen) since the introduction of the 52 multiverse.
• Post-Flashpoint, this new Earth-Prime reality was given the name Earth 33.

The Flash #179 (May, 1968)