Earth-Prime
One of the "infinite Earths," Earth-Prime was originally believed to be a world without superheroes like our "real" world, this state of affairs soon changed when the superhero Ultraa arrived. He was eventually convinced by the Earth-1 Justice League of America to leave.
Later, the Earth-2 villain Per Degaton travelled back to the 1960s and stole nuclear warheads from Cuba during the Cuban Missile Crisis; this led to a nuclear war that left 1980s Earth-Prime a radioactive wasteland, populated by hideously mutated lifeforms. This horrible timeline was undone by the combined efforts of the Justice League of America, the Justice Society of America, and the All-Star Squadron.
As the Crisis on Infinite Earths ravaged the multiverse, a last event that held Earth-Prime different from "true" reality occurred; a version of Superboy was revealed to live on the world. He was the only survivor when Earth-Prime was consumed by anti-matter.
Comments
After the Crisis, the Psycho-Pirate referred to Earth-Prime and stated that it was destroyed by a nuclear war, but he was probably confusing the "normal" Earth-Prime with its dimmer alternate timeline.
