Bob Morgan one of the doubles who was supposed to be portraying George Peppard in the train scene, fell off the train and lost an eye, an arm and a leg in the filming. One of the tragedies of the film. Shortly after, 6 years later, his wife divorces him.
This is more information about the marriage: "In 1962, Yvonne and Bob were having difficulty in their marriage. Then, while he was working in Globe, Arizona, on the set of How the West Was Won, Bob fell under a moving train and lost a leg and suffered other serious injuries. During his multi-year recovery, Yvonne put her career on hold to care for him. When the realities of their finances became apparent, she went back to work.
Although the accident initially brought the couple closer together, their marriage ended in divorce in 1968." 
The Wikipedia articles:
"How the West Was Won (film) (1962)
Stuntman Bob Morgan was seriously injured filming a gunfight on a moving train. Chains holding logs on a flatbed car broke, crushing Morgan as he crouched beside them."
"Stuntman Bob Morgan, husband of Yvonne De Carlo, was severely injured and lost a leg during an accident while filming."
|Includes CC-BY-SA content from Wikipedia's How_the_West_Was_Won_(film) article (authors)|
|Includes CC-BY-SA content from Wikipedia's Stunt article (authors)|