OK, one more 'look at the massive crowd' photo and we're done, we promise. Well, not promise. Maybe we'll do another. But they're really cool! Look at this aerial shot, showing how far the crowd expanded outwards in every direction. The area being covered by humanity here far outreaches the limits of the original festival, which didn't exactly delight the local residents. Attendees were free to roam as far and wide as they wanted - because the fences had been cut down.
When the crowds arrived for Woodstock and swamped the gates, a decision had to be made. The fences were there to keep people out, and protect the people inside, but people were climbing over them and tearing holes in them, making them unsafe. Eventually, the only thing that could be done was to completely remove them.