During the 1940s, Joan London worked for the California Labor Federation in San Francisco. She worked there over twenty years, writing speeches, reports, and the weekly newsletter. She continued to be active in the Berkeley branches of the Communist Party USA, then aligned with the Allies during WWII. She married Charles Miller in 1948. Although he was not political, Miller appears in the fat FBI file kept on Joan. She was on many leftist or union-focused mailing lists. Ironically, Charles Malamuth, no longer leftist, was an informer.