Throughout the Fifties, Mayer made donations to the Foster Parents Plan Inc. (as of 2016, Plan International), a charitable organization designed to help orphans and other children left vulnerable due to war and conflict situations. Materials here include correspondence between Mayer and two foster children in post-World War II Europe, as well as communications with Foster Parents Plan Inc. officials. Researchers interested in Mayer's contributions to post-war Europe relief efforts should also see material in this collection relating to the Cooperative for American Remittances to Europe, Inc. (CARE).