In the mid-1940s she became interested in the California Missions. In 1948 to usher in the centennial of California's Gold Rush, Stanford University Press published "Mission Tales" in 21 small booklets, one for each California mission. While they were still in galley proof, three newspapers – "The Fresno Bee", "The Sacramento Bee" and "The Bakersfield Bee", produced them as educational material in 13 episodes of "Cavalcade of California", which were transmitted into the schools via Radio KFWB. Later "Mission Tales" were republished in 7 volumes with three of the small books in each volume. Helen's daughter Muriel provided the more than 250 illustrations for the stories.