People tend to view land art as something that happened at a certain historical moment - like minimal art, which I was also very much involved with. But it still goes on. It's very much alive.

People should go to the works and experience them. Because just having an idea or picture in mind is absolutely not the experience that's necessary. Even just landing in Albuquerque or Salt Lake City or Las Vegas was immediately part of the experience. And then you'd get in a car from the airport and take these very long trips - in Michael Heizer's case, it was three hours by car to get to his work. And then there's walking around and into the piece and seeing it from different angles. The kinetic experience of being a part of it physically was very important for me.

I didn't know Michael Heizer until I was preparing for my "Earthworks" show in 1968, and somebody called and told me to look at his work. Heizer had already made land art before any of the others and was deeply into it. But he was very young and working out West, so I wasn't aware of his work until he came and showed it to me.

Art wasn't for selling. Actually, we once did have an offer on Double Negative. Things could be sold actually - everything could be for sale. But we had very few buyers. I think it was Michael Heizer who said that the point was to have a bigger canvas, and I've used that expression quite a bit. But I was thinking today that a canvas has boundaries; it has limit to it. And for earthwork, it was the very openness and feeling that there were no boundaries that made it so exciting.

People tend to view land art as something that happened at a certain historical moment - like minimal art, which I was also very much involved with. But it still goes on. It's very much alive.

I myself had lived in the San Fernando Valley many years ago, when it was a much wilder place, and we used to go walking in the wild areas. So that early experience had a lot of similarities for me to the places that Double Negative was being done.

I enjoyed cross-country road trips. And I found the work challenging because it was art that existed on the land rather than mere concepts in a gallery or photographic documentation, or any of the paraphernalia that can be used to indicate that. The art was on the land.