For "Double Negative," in 1969, Dwan gave Heizer money, sight unseen. Working partly with Dwan's gallery director, John Weber, Heizer called her from Los Angeles one day to say it was done. A few years later, Dwan bought for Heizer the first parcels of property in Garden Valley, which he chose because the land was cheap, the soil and climate were right and not much of the rest of the valley could be homesteaded. "When I visited at first Mike was living in a trailer and had a big young Mormon working for him," Dwan recalls. The road in and out was a weedy livestock trail, which sometimes got so bad in winter that Heizer would be locked in for months, seeing only a couple of sheep trailers and an occasional pickup truck. Fearful of being robbed, he surrounded the place with cyclone fencing and left only at night to get back before dawn.

Eventually he built himself a house out of cinder-block seconds. When Dwan finally saw the first Complexes, she cried. "There he is in the middle of nowhere, without an art world to talk to, without a bar where he can go find friends for support, building something much larger than anyone has ever built, knowing he is going to be criticized for grandiosity, and yet going ahead and building what he must. That takes courage."

Heizer still commuted to New York and Los Angeles, doing commissions, networking. He liked the dinners at Odeon, the parties at Chateau Marmont with movie stars -- until he decided he didn't. "They're frivolous, I'm not," he told me. "You don't control your own destiny in New York. It's fine if you trust the system and agree to move along the street in an orderly fashion. But you can't carry a weapon to protect yourself, even though it's more dangerous there than here. I find it castrating."

It has been said that the early works Heizer and Smithson and De Maria and others did outdoors seemed like a fresh start, full of promise. Nancy Holt, the sculptor who was married to Smithson and who used to be close to Heizer, recalled traveling with the two men: "To go outside into the landscape, that sense of liberation, just crossing the Hudson River, it was glorious. The mass media picked up quicker than the art media what was happening. This was when everyone was seeing the earth from outer space for the first time; 'ecology' was a new word. And when you look at the old photographs of us, you can see the joy in our faces."

That was then. Should the rail go through, Heizer now claims, he'll dynamite "City," never mind that he is building it to be indestructible for thousands of years, or that the people giving him money aren't likely to fork over another million or so dollars to destroy it and return the desert to its original condition. But with him, it has become all or nothing. Posterity isn't the next generation; it's a millennium. "Double Negative" was "the most incredible sculpture I've ever seen or done," Heizer says. "When I finished I laughed. I knew I'd done it. There was no precedent in the history of mankind."

And he did not just add his sensibility to radical art movements of the 60's and 70's. As he sees it, he single-handedly, without influence from any other living artist, started a "revolution." "I'm self-entertaining," he declares in another fervid soliloquy. "My dialogue is with myself."

The sculptor Richard Serra, Heizer's contemporary, who was an acquaintance of Heizer's during the 60's and whose own work sometimes now rivals Heizer's in size, has said: "Whoever tells you he dropped from heaven knows the opposite is equally true." Serra hasn't seen "City," but he told me that he could imagine "the work may empower people in ways that don't have to do with scale, in ways that we can't foresee. Heizer's stance is empowering because what artists do is individuate themselves, and this guy has done it to the nth degree." Of course, Heizer is not really on his own in the desert, as the nuclear train proves. There was also the MX during the 80's, he reminded me one morning. We were in his kitchen with Gracian Uhalde, his nearest neighbor, who has a ranch about 15 miles away and who works as a contractor on "City." We sat before cups of strong espresso that Heizer likes to serve in glass tumblers at the table his father built for him years ago out of mining timbers scavenged from some abandoned mine shafts in the Golden Gate Range. The MX plan was to crisscross Garden and other nearby valleys -- Coal, Dry Lake, Delamar -- with rail tracks leading to silos for moving around and hiding missiles. ("Peacekeepers," as President Reagan called them.) Mary spread an MX map over the kitchen table. It showed the valleys as a checkerboard of rail lines. "With the MX we won," Uhalde said, meaning the government decided not to go through with it. "Now they're back at it."