In 1956, the Duke starred in an epic biopic about Genghis Khan called "The Conqueror"—a casting decision that probably qualifies as one of history's greatest mistakes in and of itself. Personally, if we were cast as Genghis Khan in a film that required us to pretend Utah was the Gobi Desert and forced us to spout lines like, "I feel this Tartar woman is for me, and my blood says, take her!," we're pretty sure the shame would kill us. Sadly, however, it was more than shame that killed dozens of people involved in the movie's production.

Turns out, much of the filming for "The Conqueror" was done in Utah's Snow Canyon, about 150 miles downwind from a U.S. nuclear testing facility.

Bomb.jpgWayne, along with director Dick Powell, costars Susan Hayward, Pedro Armendáriz, and Agnes Moorehead, and additional cast and crew members, lived in the shadow of this fallout for three months. The first signs of trouble cropped up in 1963 when Powell died of lymphoma and Armendáriz killed himself after being diagnosed with terminal cancer. More cancer deaths followed: Moorehead in 1974, Hayward in 1975, and John Wayne in 1979. Although the Duke's passing was popularly attributed to his years of smoking, People magazine later muckraked records showing that no fewer than 91 of the 220 people who worked on "The Conqueror" had contracted cancer—and more than half of those had died.

20-mistaikes.jpg---This summer, mental_floss is re-running parts of "The 20 Greatest Mistaikes in History," Maggie Koerth-Baker's cover story from March-April 2007. To order the back issue, click here. To see other installments in this series, click here.