One of the best on-line resources on ths history of Wicca can be found at http://www.geraldgardner.com/History_of_Wicca_Revised.pdf You might also want to read through the information at http://www.thewica.co.uk/
And there are a number of excellent books on the history of Wicca that I would suggest. Try these:
"Triumph of the Moon" by Ronald Hutton
"Gerald Gardner, Witch" by Jack Bracelin
"Gerald Gardner and the Cauldron of Inspiration" by Philip Heselton
" Wiccan Roots: Gerald Gardner and the Modern Witchcraft Revival " by Philip Heselton
If you have any specific questions about the history of Wicca that I can help you with just drop me a line.