The papers of Henry L.V. Day are divided into five series.

Correspondence and Related Records, the first series, is divided into four subseries. The first of these, Youth and Education, contains letters, receipts, certificates, photographs, pamphlets, early papers, and mementos concerning his childhood and his life as a student at the Newman School, the University of California, and Harvard Graduate School of the Arts and Sciences, and also material relating to a European vacation in 1923. Course notes and a draft of his senior thesis also form part of this subseries. The Chronological File includes general business correspondence, including legal explanations given him by John Wourms, and correspondence from his latter years dealing with political subjects. The largest of the subseries is the Alphabetical File. It covers Henry's entire range of personal, political, professional, business, financial, avocational, and philanthropic interests, primarily in his later years. It is an alphabetical file with correspondence and other records concerning family and friends filed next to purely business records. Included are letters, memoranda, congratulatory cards and notes, typed and printed reports (both financial and narrative), lists, proxy statements, financial statements, balance sheets, minutes, press releases, clippings, longhand notes, handbills, advertisements, brochures, pamphlets, maps, and other types of records. The folders concerning Camp Neewahlu, a Camp Fire Girls camp on Kidd Island Bay which Henry donated to them, Day Mines, Inc., and East Shoshone Hospital are quite extensive. The Index: Document Files, is a bound volume containing a list of documents R.H. Sneed believed to be the most important records in recreating the lives and times of the Day family and their location in the five filing cabinets in the "inner vault of the main basement vault" of the Day Building in Wallace.

The second series is comprised of financial records. The first subseries, Ledgers and Statements, includes cash received journals, voucher registers, cash disbursed journals, and other oversize ledgers for the years 1935 to 1982. The depreciation schedule, 1957-1975, relates to real estate and personal property owned by Henry Day. The bond register, 1921-1955, contains separate listings for bonds held by Harry L. Day, Barbara Flohr Day, Henry Lawrence Day, Eleanor Day Boyce, Day Mines, Inc., and Hercules Mining Company. Also included in this subseries are Henry Day's personal financial statements for the years 1935 to 1963 and financial statements for various Day-owned companies. The second subseries contains material related to various Day family estates, and trusts set up for Day family members. Property records, including abstracts of title and appraisals for Henry's residence at 114 Cedar in Wallace, his summer home on Lake Coeur d'Alene, Laissez Faire, and the Santa Barbara Home, Las Palmas.

The third series, Technical Papers, includes correspondence and reports from consulting geologists L.C. Graton, A.C. Lawson, Rodgers Peale, and William D. Mark. Also included are reports of property examinations by E.S. Rugg and R.H. Nagell. The final item is a four volume report on assaying by Herbert Emery Samms who was employed in control assaying and engineering work for the Tamarack And Custer Mine from 1922 until his death in 1940.

Historical Material, the fourth series, includes correspondence, research material and a draft of Charles R. Stark, Jr.'s biography of Harry Loren Day, and several typescripts of John Fahey's book "Days of the Hercules", with corrections by Henry L. Day and Henry Day Ellis. Also included are newspaper clippings about the Coeur d'Alene region and some early World War I clippings which probably belonged to Harry Day. This series also includes speeches given by Henry Day to mining and civic organizations.

The final series contains photographs, certificates and plaques, and other material which did not fit into the previously designated series. The photographs are, for the most part, personal, and include a series of negatives for photo albums maintained by Henry Day. These negatives are numbered by book and pages on which the prints occur, but only the negatives are available in this manuscript group. The prints were sorted by subject, then arranged alphabetically. Occasionally a group of prints was found in a labeled envelope (e.g. Henry Day Old file), and in this case the prints were kept together and the label on the envelope used as the folder heading. Some of the subjects covered are Day family photographs, Eugene Day's hauling outfit, mine photographs, and politicians. It is obvious from the date of many of the photographs that they originally belonged to the previous generation of Day family members. Also included is Jerome Day's photograph album, and an album on Burke, Idaho given to DMI by Joseph Foley, Jr. in 1956.

The certificates include those belonging to other members of the Day family which are foldered separately from Henry's. His certificates were sorted by type, e.g. civic activities, diplomas, religious, etc., then arranged chronologically in folders. The wooden plaques were treated in a similar manner.

The remaining material in this series consists of material which did not fit into the previously established series and includes commemorative coins and bills, a January 4, 1800 copy of the Ulster gazette, telegraphic code books, a 3 volume typed index of Coeur d'Alene Mining Companies and men affiliated with the Coeur d'Alene mining industry as of January 1, 1922, and 2 reels of 16mm film on the Sunshine Mine fire, apparently part of a documentary filmed by Wolper Productions in 1972. Also included are oversize rolled maps, aerial photographs and other items, which, because of their awkward size are stored separately from the shelved boxes.

Publications, duplicate materials, vouchers, annual reports of non-Day owned companies in which Henry Day held stock, and unedited photocopies of John Fahey's manuscript were discarded. The historic maps which Day collected were added to the Special Collections map collection in order to make them more accessible to researchers. These measures, plus refoldering from legal to letter size when possible, reduced the bulk of the material by 22 feet.