As a naive tourist, I did not know this. I drove up to Sequoia National Park in March 2011 hoping to camp. The roads were plowed, with eight feet tall snow on either side of the road. I drove up to a visitor center and asked where to camp. The park ranger said I could camp anywhere I wanted. Maybe he assumed I knew what I was doing. But I did not. After walking around the parking lot for a bit, with nowhere else to go, I drove out.