 Heller's personal papers, including private correspondence and manuscripts, are preserved in parts at the Northwestern University Archives in Evanston, and in parts at the Deutsches Literaturarchiv (Schiller-Nationalmuseum) in the southwestern German city of Marbach am Neckar (Baden-Württemberg).The files of the Northwestern University Archives contain some photographs.The Library of Congress in Washington, D.C., for its part, holds facsimiles of some of his letters (in particular those addressed to Hannah Arendt and Robert B. Silvers), in addition to the sound recordings of two of his lectures, the one on 'The Modern German Mind