Earth Three is a universe parallel to Earth One and Earth Two. The name was coined by Jay Garrick. Similar to Earth Two, Earth Three has various features that are anachronistic compared to Earth One, such as the popularity of zeppelins and the Tommy gun.
After Hunter Zolomon overdosed on the Velocity drug, he crossed over into this world. While terrorizing this Earth, he soon discovered the full effects from the drug in his system. In a frenzied attempt to try to restore his original health, he overpowered the Flash of this Earth, and took him back to his Earth to take his speed to heal himself. However, for some reason it didn't work, so he imprisoned him and stole his identity to use it to give the people of his Earth hope so he could sickly rip it away.
After Barry released Jay Garrick from his prison, he went back to Earth Two with Harry and Jesse and made his way from there back to his Earth.
The Trickster from this world robbed a bank. He told the citizens inside that if they followed his instructions, he'd let them live, but he went back on his word and killed them anyways. CCPD officers dispatched to apprehend him, but Jay Garrick appeared on the scene first. Upon being confronted, the Trickster fired his Tommy gun at Garrick, but the speedster easily caught all the bullets with his helmet. As a last resort, the Trickster cuffed himself to the Flash and activated a time bomb. Fortunately, Earth One's Flash arrived, disabled the bomb, and tied up the Trickster. The police arrived moments later and took the super criminal into custody.
After Wally West of Earth One was trapped in the Speed Force by Savitar, Jay Garrick decided to sacrifice himself to take Wally's place. With Jay Garrick gone and no Flash to protect this Earth, Jesse moved here to take his place until he can return.
After Jay Garrick was released by Cisco Ramon's altered Speed Force Bazzoka, it is unknown if Jesse returned to her home Earth to allow Jay Garrick to continue protecting Earth Three as the Flash.
Known Inhabitants:
The Flash
The Trickster