Earth-1A

"We're not getting anywhere philosophizing about this! We're the only ones who know about this. Part of our power is the ability to remember discarded timelines. Like when Reverse-Flash killed us with the ol' vibrating-hand-in-the-heart, but then Barry changed time, and we were alive again. So only you and I know about Earth-1 and... let's call it Earth-1A."

- Cisco about the existence of Earth-1A to his doppelgänger

Earth-1A also designated Earth-1 by this earth's inhabitant is a universe in the Transmultiversal Multiverse.

Creation
In October 2016, this universe was created as a result of Flashpoint. This caused the existence of two twin multiverse.

Earth-27 Invasion
In late 2018, the Crime Syndicate of America opened a rift in Central City when the Anti-Matter Man entered and poisoned the universe, killing everyone except a few thousand of speedsters from their Central City who reached the rift just in time. The crime syndicate started to cause chaos until the Flash and other heroes joined forces to stop them. Green Arrow manage to pull a perfect shot at the side of the rift to close it, stopping the Anti-Matter Man from reaching this universe.

From Earth-2

 * Harry Wells
 * Zoom (Hunter Zolomon)

From Earth-3

 * The Flash (Jay Garrick)

From Earth-19

 * H.R. Wells

From Earth-27

 * Crime Syndicate of America
 * Johnny Quick (Eddie Thawne)
 * Owlman (Bruce Wayne)
 * Power Ring
 * Superwoman
 * Ultraman

From Earth-38

 * Supergirl (Kara Danvers)

Locations

 * Earth
 * United States of America
 * Central City
 * Keystone City
 * Star City
 * Krypton