The Silver Age Flash enemies all lived on Earth-One and started out as enemies of the second Flash, Barry Allen, as well as the third Flash, Wally West, and the fourth, Bart Allen, after the death of Barry Allen.
The Silver Age Flash's adversaries were all situated on Earth-One and started as foes of the second Flash, Barry Allen, including the third Flash, Wally West, and the fourth, Bart Allen, following Barry Allen’s death.