It started for beta testing in March 2005 and opened to the
general public on October 24, 2005.
Club penguin was created by a company called Rocket Snail. It was originally called Penguin Chat. PC (Penguin Chat) was originally released in a very early beta mode to the public. At this time, Disney did not support PC, so the servers running PC were somewhat basic. The max players could only be about 100 before the game would crash. Once the game was created, a lot of users complained about how many features were lacking, suck as the dojo and pet shop did nothing at all. Once Disney stepped in though, they built it into a great game that we see today. You still can see Rocket Snail's website here: http://rocketsnail.com
Hope this helps.