Viggo Mortensen committed to this movie during a busy stretch of work. When filming was delayed, he tried to beg off, asking Ed Harris to try to find another actor. Harris interviewed 20 others for the role, but they either declined or weren't right for the part. Mortensen agreed to do it, and according to Harris, "Two days before we started principal photography, Viggo shows up in New Mexico. He's ready to go. He's done research on the period. He's given really great thought to his character. He had detailed ideas about his wardrobe and his props. He was in excellent shape and good spirits, and he subsequently played Everett Hitch to perfection. Viggo Mortensen is a man of his word."
When Ed Harris reloads his Peacemaker (Colt Model 1873 Single-Action Army revolver), he realistically uses the pistol's ejector rod to push spent cases out of the cylinder. Few Hollywood actors know what the ejector rod is, and are seen in various westerns reloading SAAs by opening the loading gate and shaking the spent case out.
Viggo Mortensen fell in love with Ariadna Gil, who played his lover in this movie, and they've reportedly been together as a couple since 2009.
Originally planned as the first in a series of movies based on a series of books about Hitch and Cole.
Because the only remaining eight-gauge shotguns on the market were either too antique or too valuable to use, the movie's armorer, Gibbons Ltd., had to specially contract for replicas. Gunsmith Steve Karnes purchased three replica Colt 1878 shotguns and modified the barrels so that all three sets would have bore sizes equal to that of a real eight-gauge shotgun. The first two shotguns were designed to fire full-load 12-gauge blank rounds (one could be used while the other was cleaned or repaired from a previous shoot). The third was designed to chamber eight-gauge inert rounds and was used for reloading scenes. All three were then given identical "aged" finishes to make them appear old and used.