Lillian (Sidery) Caldwell was involved in the Los Angeles Federal Theatre Project, a theater funded by the Works Progress Administration (WPA) from 1935 to 1939. She took classes in drama and radio, and in 1963 was the host of a radio broadcast show entitled "Coffee Break". She was a member of the Waitresses, Cashiers, Checkers, Cafeteria, Fountain, and Dairy Girls' Union, Local No. 48 (Los Angeles, Calif.), as well as a member of the Social Committee of the AFL & IAM Committee for Wallace.

Malcolm Caldwell was affiliated with a number of union organizations during his lifetime. In World War II he served as Principal Engineering Aide with the United States Engineer office of the War Department (USED), and became a member of the Federation of Architects, Electricians, Chemists and Technicians (FAECT). He also maintained memberships in the Joint Anti-Fascist Refugee Committee (JAFRC), and the Oil Workers International Union. Later, he became a member of the American Federation of Labor (AFL), Congress of Industrial Organizations (CIO), and the Utility Workers Organizing Committee (UWOC). Caldwell’s political memberships included the American Peace Crusade and the Independent Progressive Party. In addition to these activities, Caldwell also wrote frequently about politics.