Earth-Prime

In the Multiverse, Earth-Prime at first appears to be the actual reality where the readers lived, DC Comics operated as a publisher, and all superheroes are fictional. However, Earth-Prime became an alternate reality in its first appearance in 179, when the Flash accidentally travels there from Earth-1 by being pushed by a creature called the Nok. The Flash, stranded, contacts DC Comics editor Julius Schwartz who helps him construct a cosmic treadmill to return to Earth-1. 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-1 and Earth-2.

In 228, Earth Prime's Cary Bates travels to Earth-1, where he discovers that the stories he writes are not only based on events on Earth-1, but he can actually influence these events as well. This power turns for the worse in 123, when Bates is accidentally transported to Earth-2. The inter-dimensional trip temporarily turns Bates into a super-villain, and he quickly kills the Justice Society of America. Luckily fellow DC writer Elliot S. Maggin, with the help of the Justice League and the Spectre, is able to restore matters on both Earths in 124.

Ultraa

Ultraa was introduced in 153 and was Earth-Prime's first super-hero.. Like Superman, Ultraa was the sole survivor of a destroyed alien world, rocketed to Earth-Prime as a baby. After his first encounter with the Justice League, Ultraa decided Earth-Prime was not ready for super-heroes and relocated to Earth-1.

Superboy

The world's second super-hero is Superboy. He first appeared in 87. This Superboy's powers first manifested around the time of the passage of Halley's Comet in 1985. Just after manifesting his powers, Superboy met Earth-1's Superman (Earth-1)Superman. Very soon thereafter Earth-Prime was destroyed in 10. Superboy escaped his universe's destruction, and later joined Earth-2's Superman, Earth-2's Lois Lane-Kent, and Earth-3's Alexander Luthor in in traveling through a portal that led them back to Earth-2.