With backing from Pohlad and Paramount Vantage in place by February 2006, Penn had just a few months to assemble a team and scout locations before shooting began that spring.

PENN: It took cumulative forces of will to make this happen. I was able to put together a sensational crew. It was like I put a call in to Special Forces for an emergency mission and everybody just went for it.

FRANK HILDEBRAND, 55, executive producer: Sean started by retracing Chris's steps and tried to hook up with as many of the real people who knew Chris as possible. One of the key characters, Wayne Westerberg, was a driver on the film.

WAYNE WESTERBERG, friend and former boss of Chris McCandless who hired him to do odd jobs at his grain elevators in Carthage, South Dakota (Westerberg, who identified McCandless's body in Alaska, still refers to his friend as "Alex"): My phone rang in the truck and it was Sean Penn. He wanted to come basically the next day to South Dakota. He asked me to come work on the movie, and I thought, What other time in my life would I be able to work on a production for a year? So I parked my truck and put everything on autopilot and ended up going with those guys last year. I worked in transportation.