In an interesting twist of fate, Brad Pitt lost out on the role of Brian McCaffrey in Backdraft (1991) to William Baldwin, who then had to be released from his contract to play the small part of J. D. in Thelma & Louise (1991) that was re-cast with Brad Pitt.
The photos of firefighters seen on the walls of the investigators office are of the Los Angeles Country fire fighters who were on scene during the filming of the fire scenes as a precautionary measure.
There are three arson victims: Donald Cosgrove, Alan Seagrave, and Jeffrey Holcomb. Cosgrove is named after the real-life Chicago fireman/author William Cosgrove who served as Robert De Niro's technical advisor for the movie. Seagrave is the name of a fire apparatus (fire and ladder truck) manufacturer. Also, the firehouse where Engine 17 and Truck 46 were quartered is the real, in-service firehouse of the Chicago Fire Department's Engine 65 and Truck 52.
There's a scene where Scott Glenn's character breaks out the windows of a Mercedes Benz that is blocking a fire hydrant in order to snake the hose through the car to access the hydrant. On the night of April 9, 2014, the Boston Fire Department was forced to break out the windows of a BMW that was blocking a fire hydrant so they could respond to an 8-alarm fire across the street from the hydrant.
The numbers of the fire companies are all "dead" numbers in the Chicago Fire Dept. Engine 17, Truck 46, Engine 24, Truck 6 (now back in service as of March 2004), and Engine 33 (referred to, not actually seen in the movie), are all out of service. The Chicago Fire Dept. has twenty-four battalions. Battalion 25 was created for the movie.
The production company totally refurbished six pieces of fire apparatuses and, upon completion of filming, donated five of them to the Chicago Fire Department, who used four of them as front-line equipment for several years, and one as a spare. The only one that was not donated to the city was the truck that was flipped over, which was totaled for that shot.
The Character of Donald Rimgale is always referred to as "Inspector" but his actual rank is Captain as evidenced by his helmet and his dress uniform. This means he is a senior inspector who probably commands others of lower rank.
Engine 17 (80-289/D-374 E8 - rehabbed to E17/51/69) used in the movie was purchased by a private individual and is currently under renovations to restore it back to its luster as E17 after several years of storage. A sister Ward LaFrance/Ranger (80-293/D-378 E49 - rehabbed to E34) was sold to a Fire Department in Pennsylvania and was refurbished into an Engine 17 clone.
The trivia items below may give away important plot points.
Many of the extras in the film are actual Chicago firefighters. A casting call was put out in a Department memo prior to the start of shooting. In addition, many suburban firemen participated in the funeral procession.
Kurt Russell plays two roles in this film as Father and Son in the McCaffrey family. In the beginning, he plays Dennis McCaffrey who was the father of Stephen and Brian. He dies in 1971 in a firefighting accident. Throughout the rest of the film, he plays Stephen McCaffrey, the oldest son of Dennis and oldest brother of Brian. He dies on his way to the hospital after falling down on a pipe with his family friend "Axe" who burns up in a chemical plant fire. He does that while finding out that Axe is responsible for the backdrafts and while Axe is on fire. In both those scenes Brian is there when both his father and brother die. Stephen and Dennis have similarities being that they look alike and dress alike. But the difference is that Dennis has his hair combed down and a mustache and Stephen has no mustache and his hair spiked up like a flattop.