Well, that depends entirely upon who you ask... there are two common versions of our history:
The first, inspirational version states that Wicca is the current revival of an ancient pre-Christian religion of Europe. According to this view, Wiccans (witches) were practicing openly until "The Burning Times" (The inquisition), when they were forced to go underground. The practices and rituals have been carefully preserved, hidden, and handed down within families for centuries. These "hidden traditions" were recently revealed to the public in the late 1940's - early '50's, leading to the modern revival of Wicca.
The second, more historically accurate version of our history is that this is a purely modern religion that had it's beginnings straight from the imagination of Gerald Gardner in the '40's - 50's and caught on like wildfire. Borrowing heavily from prior traditions of High Magick (such as Crowley) a new spiritual tradition was born, inspired from the mythologies of the past. This view doubts the claims of "direct lineage's" of unbroken traditions, but rather holds the view that Wicca is all a modern recreation inspired by the pre-Christian traditions of the past.
Although not historically accurate, I think there’s reason for teaching both versions. Many traditions have a mythological past that inspires current practice. Therefore, although historical accuracy is important to understanding who and what we are, it’s not required to support a creation myth. Regardless of whether our religion is 5000 years old or 50, it is constantly evolving and changing to suit our current needs. This is how it should be, and I see room for both Wiccan histories.
~Flame RavenHawk