What happened between the debut album and Freewheelin'?

I was just wondering about the insane jump between Dylan's first album and Freewheelin'. Like, the difference is mind blowing to me - how did he get so much better in such a short time? I mean, "Song to Woody" is fine and all, but it's not even in the same universe as something like "Hard Rain." I know Dylan sometimes hints at that whole Robert Johnson devil-at-the-crossroads thing when people ask him about this period, but does anyone know what actually went down during that time?