The Wizard of Oz is such an integral piece of Hollywood history that you might assume it was the original film adaptation of Baum’s book. But that’s not the case, according to William Stillman, film historian and coauthor (with Jay Scarfone) of The Road to Oz: The Evolution, Creation, and Legacy of a Motion Picture Masterpiece.

“The Wizard of Oz is actually a remake,” he says. “There had been two silent films previous to the 1939 version: one in 1910 and the other in 1925. The latter starred a well-known comedian named Larry Semon.” Semon’s co-star, Oliver “Babe” Hardy, would soon team up with Stan Laurel to become the internationally renowned duo of Laurel and Hardy, he adds.

The production’s wardrobe department searched local thrift stores for the perfect jacket for Professor Marvel (Frank Morgan), the itinerant con artist with a crystal ball that Dorothy (Judy Garland) meets at the beginning of the film when she runs away from home. “They wanted grandeur gone to seed,” the picture’s publicist Mary Mayer told Aljean Harmetz for her seminal 1977 book The Making of the Wizard of Oz. “A nice-looking coat, but very tattered.”

Ultimately, a Prince Albert-style coat made of black broadcloth with a velvet collar was chosen. One particularly hot day, Morgan turned the coat’s pocket inside-out and saw the name “L. Frank Baum.” Mayer said that they wired the Chicago tailor who had made the coat, and, in a notarized letter, he confirmed that it belonged to Baum. The author’s widow also identified the coat as her husband’s.

Typically, movies only have one director, but The Wizard of Oz had a series of four. “Directors worked on seven-year contracts for particular studios in those days, but were considered interchangeable workers,” says Chris Hite, a film professor at Allan Hancock College. “Producer Mervyn LeRoy initially wanted to direct the picture himself, but was convinced by MGM head Louis B. Mayer that it would be too much work on top of overseeing his producorial responsibilities.”

Instead, LeRoy hired Norman Taurog to handle directing, but quickly replaced him with Richard Thorpe who lasted only two weeks, Hite says. “Thorpe, who did a fair amount of foundational work on the film, claimed in later interviews that none of the footage from his work on the picture remained, it was all thrown out, including scenes of Dorothy with blonde hair and actor Buddy Ebsen as the Tin Man,” he explains. There was a good reason for this: according to Stillman, LeRoy dismissed Thorpe because he was dissatisfied with the raw footage he shot.

Next, renowned director George Cukor took over as a consultant during a shutdown, stepping in for three days. Though nothing was shot during his brief stint on the film, he made major creative contributions, including refining the looks for Dorothy and Margaret Hamilton’s Wicked Witch of the West.

Victor Fleming then took over as director and oversaw many of the iconic aspects of the film, including the twister sequence and is credited with the sepia toned counterbalance to the color sequences, Hite says. “After several months, Fleming was reassigned to Gone with the Wind, and the director originally assigned to that picture, King Vidor, ended up finishing The Wizard of Oz,” he notes. According to Hite, switching directors on a film project wasn’t uncommon at the time. “The studio system contracts allowed the studio to interchange directors at will,” he says.

There’s a longstanding rumor that asbestos was used as artificial snow in the poppy field scene of the movie. Though it’s now a known carcinogen, asbestos was widely utilized in the 1930s for its insulation and fire-proof properties, but according to Stillman, it didn’t double for snow in the film. “MGM makeup artist Charles Schram distinctly recalled that the artificial snowflakes were created using crushed gypsum, a mineral used in plaster of Paris,” he explains. “It was his job to pick the gypsum particles out of the wig for Judy Garland and Bert Lahr’s Cowardly Lion mane.”

Asbestos was, however, used in another part of the movie. In the scene where the Wicked Witch of the West lights the Scarecrow (Ray Bolger) on fire, the actor wore a version of his costume made from asbestos. “Men with wet blankets and fire extinguishers stood out of camera range in case of a mishap,” Stillman says, “Every time the Scarecrow moved, Bolger recalled, the straw sprouting from holes in his costume had to be rearranged to exactly match the previous shot.”

Because of the massive sets and the primitive Technicolor film the movie was shot on, the set of The Wizard of Oz had to be extremely well-lit. There was an enormous bank of more than 150 36-inch overhead lights installed to mimic natural sunlight, which, like the real thing, gave off a lot of heat.

“We borrowed every unused arc light in Hollywood,” cinematographer Harold Rosson said in The Making of the Wizard of Oz. “It was brutally hot. People were always fainting and being carried off the set.” The incredibly bright rays also left several members of the production with “klieg eyes”—a condition that causes pink inflammation and swelling.

The best air conditioning available at the time was no match for the on-set lighting, so when the temperature became unbearable, production would stop for two or three hours while the actors caught their breath outside.

After confronting Dorothy in Munchkinland, the Wicked Witch of the West (Margaret Hamilton) disappears in a cloud of fire and smoke. Her carefully choreographed exit involved a trap door and an elevator, but the fire effect went off too soon on one of the takes, leaving Hamilton with first-degree burns on her face, and second-degree burns on her hands, according to an MGM inter-office memo.

The skin on one of her hands had been burned off from her wrist to her fingernails. Typically, the studio’s doctor would have covered Hamilton’s burns in a salve, but because the green makeup she was wearing on her face and hands contained copper, it was toxic and had to be removed first—with alcohol, which would also act as an antiseptic. “I stood it as long as I could,” Hamilton said in The Making of the Wizard of Oz. “And then I said, ‘I’m going to have to scream.’” But she didn’t scream, and sat calmly until her makeup was off. “But I’ll never, as long as I live, have anything that took my breath away like that pain,” she added.

According to MGM publicity, the studio “rented” 300 birds from the Los Angeles Zoo so that Fleming, the director du jour, could select a few to be in the background of the apple orchard scene. These birds included golden pheasants, a South American toucan, a Sarus crane and an African crane—one of which can be seen in the film. “When Dorothy, the Scarecrow and the Tin Man skip down the yellow brick road, a Sarus crane makes its presence known by spreading its wings,” Stillman says.

However, over the years, people mistook the movement of that crane for something much darker. “Since the 1970s, there’s been a rumor of a stagehand wandering into the background of one movie scene,” he explains. “In recent times, that myth has become a Munchkin hanging from a tree.”

But Stillman says that a bird is behind the confusion. “Besides, it's simply not possible that none of the over 50 staff behind the camera would’ve ignored anything ill-fated,” he adds.