Earth-1 also known as New Earth or Earth-Prime is the center of the Multiverse which spawned the rest of the multiverse following Infinite Crisis. This is the original home of the speedster Velocity (Earth-Prime).
History of the Speed Force
It was stated that the Speed Force splintered from this earth when the multiverse was created after Infinite Crisis, and as a result weakened as each new earth birthed a speedster. As a way to fix the rupture and rejoin the speed force, it created an avatar, by granting one last person a link but a pure link. This avatar would work to reunite the fractured speed force, and his name would be Velocity.
Prior to his interdimensional traveling, this earth was conquered by Velocity, having lost most of its core heroes. This was said to be the result of the systematic elimination of all other Speed Force users on his earth and the subjugation of the Speed Force itself, however the speed force was never subjugated it choose Velocity to wield it in order to reunite itself across the multiverse. As such, Velocity was able to take on heroes the likes of Superman, Wonder Woman and the entire Green Lantern Corps. With the defenders defeated,he vanished, vowing to be the fastest in the multiverse.