Jagger made his breakthrough with his portrayal of Brigham Young in "Brigham Young" (1940) at 20th Century Fox, alongside Tyrone Power for director Henry Hathaway. He was cast on the basis of his performance in "Missouri Legend". According to George D. Pyper, a technical consultant on the film who had personally known Brigham Young, Jagger not only resembled Young, he also spoke like him and had many of his mannerisms. Thirty-two years later, in 1972 he was baptized a member of the Church of Jesus Christ of Latter-day Saints.