Robertson, who was best known for his role of special agent Jim Hardie in the NBC television series TALES OF WELLS FARGO from 1957-1962, died on Tuesday, the hospital said.
The "Sitting Bull" star had been in poor health for about two years and had a cancer diagnosis last week, his niece, Nancy Love Robertson, told The Oklahoman newspaper.
Born Dayle Lymoine Robertson in Harrah, Oklahoma, in 1923, the actor attracted the attention of Hollywood agents after a Los Angeles photographer posted his photo in a display window.