Of all the locations Penn had to scout, the remote spot in Alaska where McCandless spent his final months proved to be the most difficult to replicate. He started by visiting the real bus, which still sits in the wilderness west of Healy.

PENN: We went in the winter on snow machines. [The bus was] in exactly the same state. The most impacting thing is that [McCandless's] boots are still sitting there on the floor and his pants are still there folded, with the patches he sewed into them. As a story that I'd followed for so long, that was a pretty big moment... It was very moving, but I was also there to work. I knew I wasn't going to shoot there. It would have been obnoxious, a kind of rape of the area to have a whole crew there. I was going there to make a pilgrimage but also to find a reference. It affirmed for me that what I had in my head was quite accurate. Our place is an approximation.

We had a scout by the name of John Jabaley—he was the point man to find our location. We searched for over a month. It was a ton of time walking in the snow and trudging and getting cold and wet and frustrated. I was getting to the point where I was wanting to take it out on John, because we hadn't found what I wanted. But that night he came and said, "I think I might have found it." So we took snowmobiles, and as we approached I could see that this is what I'd had in mind. The hill from the river was dead on. And just as we got to the top, where we eventually placed our bus, there were three moose. And I just said, "This is it."

WESTERBERG: The real bus was a 1942 International. Those had so much iron in them that if they were in the States they'd already have been scrapped. But it costs so much to haul one in Alaska that it's cheaper to let it rot in a field. And sure enough, we found two of them up there.