The movie was loosely inspired by the story of the mare Mariah's Storm. She was a promising filly, who was being pointed towards the Breeder's Cup Juvenile Fillies in 1993, but then broke her cannon bone. She recovered, and later won some graded races. She started in the 1995 Breeder's Cup Distaff, and finished ninth. She was owned by Thunderhead Farms, and trained by Don Von Hemel. She's now known mostly for being the dam of Giant's Causeway.
Dakota Fanning worked on three other major projects at the same time as this film. They were War of the Worlds (2005), Hide and Seek (2005), and Nine Lives (2005).
Kurt Russell filmed this simultaneously with Sky High (2005). He later said it was too taxing traveling back and forth between sets and different characters quickly, and probably would not allow himself to do that again.
The role of Cale Crane was originally written for a boy. The role was changed specifically so that Dakota Fanning could play it. (The first script that was sent to Fanning actually had the word "boy" in the character description.)