The town of Daylight, Indiana, is a real place, although none of the movie was actually filmed there. Most of it was filmed in the nearby towns of Boonville, Newburgh, New Harmony, and primarily Evansville.
During the filming of the scene wherein the CPS team busts into a rundown apartment to save a child with rabies, the neighbors actually believed it was real and called the SWAT team in on the filmmakers.
Because of the subject matter of demonic possession, a prayer group formed in Evansville, Indiana, where most of the film was shot in an effort to shut down the production.
The Irons family was originally a mother and father and their daughter Sydney. However, due to casting limitations, the father character was changed to an older sister.
The original cut of the film was almost three hours long.