The papers of Henry L.V. Day span the years 1870 to 1985, with the bulk of the material covering the years 1920 to 1982. Included are correspondence, financial records, technical reports, historical material, including typescripts for two books on the Days, photographs, certificates and plaques, and other material. As the dates indicate, some of this material originally belonged to Henry's father, but was kept by Henry in his files for reference.