Some of the material in this record group was in unlabeled or poorly labeled three ring binders, and other material was in well-labeled folders. Since there appeared to be no order to the received arrangement, a series order based on format was imposed during processing.

The first series contains the material which was removed from the three-ring binders. Since most of the binders were not labeled or had one or two word labels, these were given broad subject headings, e.g. Indians, Nez Perce; Mining; Florence, Idaho; then alphabetized using the name, if any on the binder, followed by a brief description of the type of material (handwritten notes, photocopies, etc.). If there was no title on the binder only a description of the type of material was used.

The second series contains the material which was in labeled folders; it is divided into two subseries, letter size and legal size. These are also arranged alphabetically by folder heading, with an occasional description of contents. This series contains correspondence, both incoming and outgoing, about Olson's collecting activities as well as photocopies, handwritten excerpts from published sources, newspaper clippings, and photographs.

Olson's bibliography and note cards are in series three. These are on 5x8 pieces of paper and are arranged alphabetically or, as in the case of the Nez Perce war of 1877, chronologically.

Material in three ring binders was removed from the binders and placed in acid-neutral folders. Duplicate photocopies were discarded, as were carbon copies of the handwritten notes. Also discarded were the handwritten drafts of letters when the carbon-typed copy was present. USGS maps not in individual folders were sent to the gifts librarian for evaluation as possible additions to the University Library's map collection. This reduced the records by 2.5 cubic feet.