The native of Mix Run, Pa., became a star with his first feature, 1910’s “Ranch Life in the Great Southwest.” An expert shot, cattle wrangler and horseman, Mix made some 160 cowboy silent Saturday matinee films in the 1920s always playing the man in the white hat who saved the day. Even his trusty steed Tony “The Wonder Horse” became a superstar receiving countless fan mail from kids. In 1932, he returned to films, making nine talkies at Universal. His last screen appearance was in the 1935 15-...