- Daveigh Chase, Amber Heard and Evan Rachel Wood auditioned for the role of Tracy but lost to Kristen Stewart.
- Emile Hirsch lost 40 pounds to play his role.
- Brian H. Dierker was originally hired as the technical consultant for the white-water rafting scenes. Sean Penn cast him as Rainey after Emile Hirsch suggested him for the role.
- Sean Penn once envisioned Leonardo DiCaprio as Christopher McCandless and Marlon Brando as Ron Franz when he first became interested in making the film.
- Shot entirely on location.
- No stunt-men or doubles were used for Emile Hirsch, including the scenes where Chris goes through river rapids, confronts a grizzly bear or rock-climbs.
- Eddie Vedder agreed on the spot when Sean Penn called him to ask to do the soundtrack, before he knew anything about the film.
- Sean Penn waited 10 years to make the film to make sure he had the approval from the McCandless family.
- The production made four separate trips to Alaska in order to film during different seasons.
- The role of Jim Gallien, the Alaskan who gave Chris the rubber boots in the opening scene, is played by the real Jim Gallien.
- According to the DVD behind the scenes, the moose that is shot and killed by Christopher was actually roadkill found on the Alaskan highway.
- The watch Emile Hirsch wears in the movie is Christopher Johnson McCandless' real life watch, given to him as a present.
- During the making of the film, Sean Penn needed wolves and went as far as hiring "Wolf Country USA" to lease the wolves used in production. Prior to, during and after filming, Penn was seen playing "kissy face" with several of the wolves and spent hours feeding, playing with and petting them. Several of the wolves are still alive and on display at Wolf Country USA in Palmer, Ak.
>>> WARNING: Here Be Spoilers <<<
Trivia items below here contain information that may give away important plot points. You may not want to read any further if you've not already seen this title.
- SPOILER: The note that Christopher McCandless tacked to the bus actually said, "S.O.S. I need your help. I am injured, near death, and too weak to hike out of here. I am all alone, this is no joke. In the name of God, please remain to save me. I am out collecting berries close by and shall return this evening. Thank you, Chris McCandless. August?" The note shown in the film was a page from one of his "journals."
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