Originally, Roland Sharp (Tommy Lee Jones) was to be a FBI agent working in Virginia, but upon receiving the script, Jones suggested that Texas would be a great location for the film. After the producers arrived, they decided to shoot the movie there, and as a consequence, made the main character a Texas Ranger.
The Hex is an actual University of Texas tradition, enacted before the annual Thanksgiving game against Texas A&M University. The Texas A&M Aggies had their own pre-game tradition, the Bonfire, but after a combination of factors caused a collapse in 1999, killing twelve students, the tradition is no longer University-sponsored, it is, however, still organized by the student body, and done off-campus.
The finale of the movie is supposed to take place at the Eagle Pass crossing. In actuality, the crossing between Eagle Pass and Piedras Negras is in the middle of town, crossing a bridge that spans the Rio Grande. The "border crossing" the characters approach, in no way resembles the real Eagle Pass crossing.
A scene shown in the trailer, but deleted from the final film, reveals that Anne and Teresa escaped (to go out for the night) by crawling through the massive air conditioning unit that was installed on the house.
The trivia item below may give away important plot points.
Is the first movie to have the permission from the University of Texas at Austin, to use well-known UT symbols including: the UT tower (lit in orange and white - traditional lighting when a football game is won), Bevo (the longhorn mascot), UT cheerleaders, UT band, UT spirit organizations, and the UT Texas Exes.