I'm vaguely familiar with Superman's history. I know that Silver Age Superman, for instance, is crazily overpowered, being able to sneeze galaxies into oblivion and withstand a barrage of energy equal to thousands of suns. This is a stark contrast to what I know about Golden Age Superman, who is super strong and fast, but far more toned down compared to his later self.
I was wondering, when did this massive power creep happen? Was it gradual, or was Superman avoiding being shocked by power lines one issue and juggling planets the next? Either way, when did we first start seeing Superman evolve into the demi god he's known as being in the Silver Age? Any particular story to look at?